Missing changelog entry for previous commit: Add gmonster-{1,2} perf testcases.

Missing changelog entry for previous commit: Add gmonster-{1,2} perf testcases.

These testcases are mocks of real programs.
GDB doesn't care what the programs do, they just have to look
and/or behave like the real program.
These testcases exercise gdb when debugging really large programs.
E.g., gmonster-1 has 10,000 CUs, and gmonster-2 has 1000 shared libs
(which is actually a little small, 5000 would be more accurate).

gdb/testsuite/ChangeLog:

	* gdb.perf/lib/perftest/utils.py: New file.
	* gdb.perf/gm-hello.cc: New file.
	* gdb.perf/gm-pervasive-typedef.cc: New file.
	* gdb.perf/gm-pervasive-typedef.h: New file.
	* gdb.perf/gm-std.cc: New file.
	* gdb.perf/gm-std.h: New file.
	* gdb.perf/gm-use-cerr.cc: New file.
	* gdb.perf/gm-utils.h: New file.
	* gdb.perf/gmonster-null-lookup.py: New file.
	* gdb.perf/gmonster-pervasive-typedef.py: New file.
	* gdb.perf/gmonster-print-cerr.py: New file.
	* gdb.perf/gmonster-ptype-string.py: New file.
	* gdb.perf/gmonster-runto-main.py: New file.
	* gdb.perf/gmonster-select-file.py: New file.
	* gdb.perf/gmonster1-null-lookup.exp: New file.
	* gdb.perf/gmonster1-pervasive-typedef.exp: New file.
	* gdb.perf/gmonster1-print-cerr.exp: New file.
	* gdb.perf/gmonster1-ptype-string.exp: New file.
	* gdb.perf/gmonster1-runto-main.exp: New file.
	* gdb.perf/gmonster1-select-file.exp: New file.
	* gdb.perf/gmonster1.cc: New file.
	* gdb.perf/gmonster1.exp: New file.
	* gdb.perf/gmonster2-null-lookup.exp: New file.
	* gdb.perf/gmonster2-pervasive-typedef.exp: New file.
	* gdb.perf/gmonster2-print-cerr.exp: New file.
	* gdb.perf/gmonster2-ptype-string.exp: New file.
	* gdb.perf/gmonster2-runto-main.exp: New file.
	* gdb.perf/gmonster2-select-file.exp: New file.
	* gdb.perf/gmonster2.cc: New file.
	* gdb.perf/gmonster2.exp: New file.