Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Revert changes that ocassionally got into r241192.

Pointy hat to: me

MFC: r241002

Fix pseudo checksum calculation.

This fixes ipfilter w/ network controllers that implement only
partial rx csum offloading.

PR: 106438
Obtained from: upstream

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Source changes to allow building a cross-debugger. Move solib.c and
solib-svr4.c to the MD makefiles because they are native files for
alpha and sparc64, but target files for amd64, i386 and ia64.

Note that kgdb(1) does not yet build as a cross-debugger due to
libkvm.

Initialize thread_db module.

Add bmake glue for gdb 6.1.1. Supports alpha, amd64, i386, ia64
and sparc64.

Note that the debugger doesn't support threading, nor kernel
debugging yet.