[PATCH 0/2 ] PowerPC: fix for gdb.reverse/finish-precsave.exp and gdb.reverse/finish-reverse.exp

[Carl Love]

Tom, Ulrich, Bruno, Pedro, GDB maintainers:

Per the feedback on the single patch to fix the gdb reverse-finish
command, I have split the patch into two patches.  

The first patch moves the step_until proceedure from gdb.reverse/step-
indirect-call-thunk.exp to gdb/testsuite/lib/gdb.exp and renames it
repeat_cmd_until.  The new repeat_cmd_until will be used in a new test
case for the second patch.

The second patch contains the changes to GDB to fix the behavior of the
reverse-finish command on PowerPC.

The changes to gdb.reverse/step-indirect-call-thunk.exp so the test
will not run on PowerPC were dropped per the comment from Tom stating
that commit 2ef339e38f5 ("[gdb/testsuite] Require istarget x86*
in gdb.reverse/step-indirect-call-thunk.exp") takes care of restricting
the test case to only run on X86.

The wording in file gdb/infcmd.c for the PowerPC fix was updated per
Bruno's feedback.

Thanks for all the feedback.  Please let me know if the patch series is
acceptable for mainline.

                             Carl