3 patches, aiming to improve PE/COFF support:
- First patch fix symbol reading (invalid header size from sizeof() == 20 != 18, and various bugfixes such as invalid skipping of auxiliary symbols, 4 bytes shift from beginning, etc...).
- Second patch add image_base to section vmaddr offset so that VM addr is in image_base space.
- Third patch add support for DWARF section in PECOFF (taken from ELF counterpart), since they are generated by gcc/clang under windows.

llvm-svn: 184153