- fixed mingw and cygwin env detection (was always shadowed by _WIN32 macro detection, and __MINGW__ macro check was wrong to begin with) - cosmetic cleanups for consistency - added runtime detection to dyncall_macros.h to handle some edge cases - fixed detection of native thiscall callconv for builds not using MSVC but using (or adhering to) the MSVC runtime (e.g. ReactOS' MinGW based RosBE)

Daniel Adler <dadler@uni-goettingen.de>
Tassilo Philipp <tphilipp@potion-studios.com>
Olivier Chafik <olivier.chafik@gmail.com>
Erik Mackdanz <erikmack@gmail.com>
Masanori Mitsugi <mitsugi@linux.vnet.ibm.com>
Bernhard Urban-Forster <beurba@microsoft.com>