rxdebug: Remove rxdumptrace.c

rxdebug: Remove rxdumptrace.c

Ever since it was introduced in commit 8bc58a3d
(macos-10-6-support-20090216), rxdumptrace.c appears to have been
unused. While we do build a binary called rxdumptrace, we build it
from src/rx/rx_trace.c, not from rxdumptrace.c (which appears to be a
copy of the relevant portions of rx_trace.c).

Also remove rxdumptrace from src/rx/.gitignore, since the binary is
built in src/rxdebug/, not in src/rx/. While we're here, remove the
other entries in src/rx/.gitignore (rxperf and rxdebug), since those
are also built in different directories.

Change-Id: Ide816979168dcf70358f39db035ce16ef6c1dd17
Reviewed-on: https://gerrit.openafs.org/14748
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Cheyenne Wills <cwills@sinenomine.net>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>