gdb/testsuite: Make test names unique in gdb.reverse tests

Make test names unique in the gdb.reverse tests.  On my local machine
this removed 825 duplicate test names.  It is possible that different
setups might still encounter some duplicates.

gdb/testsuite/ChangeLog:

	* gdb.reverse/break-precsave.exp: Make test names unique.
	* gdb.reverse/break-reverse.exp: Likewise.
	* gdb.reverse/finish-precsave.exp: Likewise.
	* gdb.reverse/finish-reverse.exp: Likewise.
	* gdb.reverse/machinestate-precsave.exp: Likewise.
	* gdb.reverse/machinestate.exp: Likewise.
	* gdb.reverse/readv-reverse.exp: Likewise.
	* gdb.reverse/recvmsg-reverse.exp: Likewise.
	* gdb.reverse/sigall-precsave.exp: Likewise.
	* gdb.reverse/sigall-reverse.exp: Likewise.
	* gdb.reverse/step-indirect-call-thunk.exp: Likewise.
	* gdb.reverse/watch-precsave.exp: Likewise.
	* gdb.reverse/watch-reverse.exp: Likewise.