Build MinGW client library using gyp-generated Makefile

Make what it's possible to make with gyp for MinGW.

Tools which rely on DIA (dump_syms, ms_symbol_server_converter) cannot be built
for MinGW.

In theory it should be possible to build symupload, because it doesn't depend on
DIA, but it depends on the common_windows_libs, which does have a dependency on
DIA.

v2:
Use configure to find WINDRES
Use a default debug-id of all zeros when no CV record is present

This lets us do something slightly useful with current binaries
which are produced without a CV record, but there is no guarantee
that the actually match.
Increase RA scanning to 60 words

http://code.google.com/p/google-breakpad/issues/detail?id=452
Use __USE_MINGW_ANSI_STDIO for MinGW build

Use __USE_MINGW_ANSI_STDIO for ANSI C99 compatible implementation of printf()
and friends on MinGW
Provide a working strtok_r for MinGW

Emulating it using strtok will not work as re-entrancy is required
Add a README.md with notes on what is left to do