This adds the PPC architecture variants for Mach-O libbacktrace.
With this (as for X86 and Arm) when dsymutil is run on the binary
we get a basic usable backtrace.
Testsuite results on powerpc-apple-darwin9 are the same as for X86:
* btest fails (TBC why)
* dwarf5 tests fail because dsymutil does not handle that so far.
libbacktrace/ChangeLog:
* macho.c (MACH_O_CPU_TYPE_PPC): New.
(MACH_O_CPU_TYPE_PPC64): New.
Add compile-tests for powerpc to the Mach-O variants.
Close#55
