ddb: New db_stack_trace_print_ra.

Takes an optional extra argument for the return address so that the
stack parser has a chance to use instruction-dependent interpretation
of the frame to find parent frames.

Implemented only on Alpha for now, which needs it. Other
architectures just ignore the extra argument.

PR port-alpha/57716

XXX pullup-10
XXX pullup-9
XXX pullup-8

KNF: The function type must be declared on a line by itself.

need <sys/param.h> for COHERENCY_UNIT

branches: 1.9.16;
Merge the [pgoyette-compat] branch

branches: 1.8.2;
Add missing $NetBSD$ comment at the beginning.

branches: 1.7.2;
Opt to print a backtrace on panic by default with the intention of improving bug reports.
Instead of relying on ddb.onpanic=2, introduce a new sysctl called dumpstack to handle this.
via <jmcneill> channeled through <mrg> on tech-kern[1]

[1] https://mail-index.netbsd.org/tech-kern/2018/02/15/msg023103.html

- add ddb.panicstackframes to avoid scrolling the interesting parts of panic
stacktraces off.
- change valuep to void * to avoid casts
- sort and use c99 initializers in variables array

Revert printf return value change.

[syzkaller] Cast all the printf's to (void *)
> as a result of new printf(9) declaration.

branches: 1.3.4;
add a return in the panic message

branches: 1.2.2; 1.2.4;
need <sys/types.h> for various crap that other headers use (pid_t etc).

Move the DDB-specific part of vpanic() to a new db_panic() function,
defined in ddb/db_panic.c and declared in ddb/ddbvar.h. No functional
change.

The copyright years in db_panic.c are the years in which changes were
made to the code that has now been moved to db_panic.c. No pre-NetBSD
copyright notice is needed because revision 1.12 of subr_prf.c had only
the trivial "#ifdef DDB \\ Debugger(); \\ #endif"

KNF: The function type must be declared on a line by itself.

need <sys/param.h> for COHERENCY_UNIT

branches: 1.9.16;
Merge the [pgoyette-compat] branch

branches: 1.8.2;
Add missing $NetBSD$ comment at the beginning.

branches: 1.7.2;
Opt to print a backtrace on panic by default with the intention of improving bug reports.
Instead of relying on ddb.onpanic=2, introduce a new sysctl called dumpstack to handle this.
via <jmcneill> channeled through <mrg> on tech-kern[1]

[1] https://mail-index.netbsd.org/tech-kern/2018/02/15/msg023103.html

- add ddb.panicstackframes to avoid scrolling the interesting parts of panic
stacktraces off.
- change valuep to void * to avoid casts
- sort and use c99 initializers in variables array

Revert printf return value change.

[syzkaller] Cast all the printf's to (void *)
> as a result of new printf(9) declaration.

branches: 1.3.4;
add a return in the panic message

branches: 1.2.2; 1.2.4;
need <sys/types.h> for various crap that other headers use (pid_t etc).

Move the DDB-specific part of vpanic() to a new db_panic() function,
defined in ddb/db_panic.c and declared in ddb/ddbvar.h. No functional
change.

The copyright years in db_panic.c are the years in which changes were
made to the code that has now been moved to db_panic.c. No pre-NetBSD
copyright notice is needed because revision 1.12 of subr_prf.c had only
the trivial "#ifdef DDB \\ Debugger(); \\ #endif"

need <sys/param.h> for COHERENCY_UNIT

Merge the [pgoyette-compat] branch

branches: 1.8.2;
Add missing $NetBSD$ comment at the beginning.

branches: 1.7.2;
Opt to print a backtrace on panic by default with the intention of improving bug reports.
Instead of relying on ddb.onpanic=2, introduce a new sysctl called dumpstack to handle this.
via <jmcneill> channeled through <mrg> on tech-kern[1]

[1] https://mail-index.netbsd.org/tech-kern/2018/02/15/msg023103.html

- add ddb.panicstackframes to avoid scrolling the interesting parts of panic
stacktraces off.
- change valuep to void * to avoid casts
- sort and use c99 initializers in variables array

Revert printf return value change.

[syzkaller] Cast all the printf's to (void *)
> as a result of new printf(9) declaration.

branches: 1.3.4;
add a return in the panic message

branches: 1.2.2; 1.2.4;
need <sys/types.h> for various crap that other headers use (pid_t etc).

Move the DDB-specific part of vpanic() to a new db_panic() function,
defined in ddb/db_panic.c and declared in ddb/ddbvar.h. No functional
change.

The copyright years in db_panic.c are the years in which changes were
made to the code that has now been moved to db_panic.c. No pre-NetBSD
copyright notice is needed because revision 1.12 of subr_prf.c had only
the trivial "#ifdef DDB \\ Debugger(); \\ #endif"

Merge the [pgoyette-compat] branch

Add missing $NetBSD$ comment at the beginning.

branches: 1.7.2;
Opt to print a backtrace on panic by default with the intention of improving bug reports.
Instead of relying on ddb.onpanic=2, introduce a new sysctl called dumpstack to handle this.
via <jmcneill> channeled through <mrg> on tech-kern[1]

[1] https://mail-index.netbsd.org/tech-kern/2018/02/15/msg023103.html

- add ddb.panicstackframes to avoid scrolling the interesting parts of panic
stacktraces off.
- change valuep to void * to avoid casts
- sort and use c99 initializers in variables array

Revert printf return value change.

[syzkaller] Cast all the printf's to (void *)
> as a result of new printf(9) declaration.

branches: 1.3.4;
add a return in the panic message

branches: 1.2.2; 1.2.4;
need <sys/types.h> for various crap that other headers use (pid_t etc).

Move the DDB-specific part of vpanic() to a new db_panic() function,
defined in ddb/db_panic.c and declared in ddb/ddbvar.h. No functional
change.

The copyright years in db_panic.c are the years in which changes were
made to the code that has now been moved to db_panic.c. No pre-NetBSD
copyright notice is needed because revision 1.12 of subr_prf.c had only
the trivial "#ifdef DDB \\ Debugger(); \\ #endif"