[DynInst_API:] commit: bring master up to date with VEX branch, and myriad bug fixes

[Bill Williams <bill@xxxxxxxxxxx>]

* emitElf64 class is now the authoritative emitter for rewriting ELF 
binaries. Old emitElf class is deprecated.
* VEX handling for x86 brought up to latest stable point; supports VEX2, 
VEX3, EVEX, SHA512.
* Added preliminary support for building Dyninst with gcc 5.x; this 
currently forces everything to the old ABI. This will soon become a 
configure-time option.
* Assorted bug fixes in tail call parsing.
* x86 instruction decoding should now be thread-safe.
* Optimized loop analysis.
* DWARF-derived source file names should avoid string copies and be 
properly deallocated when their associated Symtab is destroyed (and not 
before).
* Applied a series of patches from Peter Foley:
- Builds using libcxx now supported
- getFunctionRef should now work properly
- Assorted CMake fixes, including proper respect for make -j
* Dyninst can now be built to parse little-endian PPC binaries. This 
will become an automatic feature rather than a build-time decision in 
the near future.
* PIE binaries should rewrite cleanly; this has been verified on only a 
limited set of platforms. Broader testing is encouraged.
As always, bug reports are welcome on-list as well as in my personal inbox.

--bw