tools: Automated cleanup of cdefs and other formatting

Apply the following automated changes to try to eliminate
no-longer-needed sys/cdefs.h includes as well as now-empty
blank lines in a row.

Remove /^#if.*\n#endif.*\n#include\s+<sys/cdefs.h>.*\n/
Remove /\n+#include\s+<sys/cdefs.h>.*\n+#if.*\n#endif.*\n+/
Remove /\n+#if.*\n#endif.*\n+/
Remove /^#if.*\n#endif.*\n/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/types.h>/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/param.h>/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/capsicum.h>/

Sponsored by: Netflix

Remove $FreeBSD$: two-line .h pattern

Remove /^\s*\*\n \*\s+\$FreeBSD\$$\n/

netmap: Fix compiler warnings in tools

- Remove write-only variables, or hide them in cases where their use is
conditional or commented out.
- Check for errors from cmd_apply() in nmreplay.
- Use ANSI C definitions.

Reviewed by: vmaffione
MFC after: 2 weeks
Sponsored by: Klara, Inc.
Differential Revision: https://reviews.freebsd.org/D38752

netmap: nmreplay: switch to libnetmap

Use the newer libnetmap (included in base) rather than the older
nm_open()/nm_close() defined in netmap_user.h

MFC after: 3 days

netmap: tools: fix several compiler warnings

MFC after: 1 week

netmap: nmreplay: import various fixes from upstream (2704a51839906)

Changelist:
- General reformatting
- Fix packet duplication in cons(). Whenever cons() reached the
burst limit it would send all pending packets without advancing
head. This caused the last injected packet to be sent again in
the next round.
- Fix full-speed transmissions after first loop.

MFC after: 3 days

Import the current version of netmap, aligned with the one on github.

This commit, long overdue, contains contributions in the last 2 years
from Stefano Garzarella, Giuseppe Lettieri, Vincenzo Maffione, including:
+ fixes on monitor ports
+ the 'ptnet' virtual device driver, and ptnetmap backend, for
high speed virtual passthrough on VMs (bhyve fixes in an upcoming commit)
+ improved emulated netmap mode
+ more robust error handling
+ removal of stale code
+ various fixes to code and documentation (some mixup between RX and TX
parameters, and private and public variables)

We also include an additional tool, nmreplay, which is functionally
equivalent to tcpreplay but operating on netmap ports.