Merge remote branch 'ramsay/dev'

* ramsay/dev:
  Add a pack index 'virtual function' to fetch an index entry
  Add a pack index 'virtual function' to search by file offset
  Change the interface of the pack index search function
  Add an 64-bit offset table index bounds check for v2 pack index
  Add a minimum size check when opening an v2 pack index file
  win32: Add separate MinGW and MSVC compatability header files
  Makefile: Add support for custom build options in config.mak file
  Fix some coding style issues

diff --cc Makefile
Simple merge

diff --cc src/common.h
Simple merge