gdb: Add PowerPC support to gdb.dwarf2/frame-inlined-in-outer-frame

This patch adds an #elif defined for PowerPC to setup the exit_0 macro.
This patch addes the needed macro definitionald logic to handle both elfV1
and elfV2.

The patch has been successfully tested on both PowerPC BE, Powerpc LE and
X86_64 with no regressions.