Fixed the use of addr2line to discover the separator symbol.

In systems where addr2line has a version greater than 2.22 pprof fails
in discover the separator symbol (_fini). This patch identifies if
addr2line can find the symbol, otherwise pprof uses objdump to recover
a address that addr2line's newer versions can recognize as the separator
function.
Fixed the way that pprof packed profile data in BE.

pprof was writing profile data in a way that only works for little-endian
files, this patch verifies if the system is big-endian and writes packed
data correctly.
Fixed getpc_test for ppc64 LE.

This patch fixes the problem with the test about get the pc on ppc64
Little Endian machines.
Fixed issues with heap checker on PPC64 LE.

Fixed the wrapper for the syscall sys_clone and the test for heap
checker on PPC64 LE. Both use the ODP structure, which is only
used on BE architectures.
Fixed heap checker test.

This patch changes the way that heap checker test identifies the
architecture's endianness. The test was using _Call_Elf to know if the
machine is Big Endian, but the _Call_Elf not always is defined in ppc64
BE and always is defined in LE machines.
Merge with fixes for Powerpc 64-bit.

This merge have fixes for the profiler, heap checker, heap profiler
and its tests.

There was a conflict in getpc_test.cc because both branches fixed it.