Slight tweaking to Makefile to get examples to build for mingw.

Pre-built binaries included for convenience:

  hello.exe
  mongoose.dll
  mongoose.exe
  mongoose.lib
  post.exe
  upload.exe
  websocket.exe

Instructions for building Via msys.bat:

  $ cd <dir-to-unzipped-mongoose>

  $ mingw32-make.exe clean # WARNING: will erase .exe, .dll, .lib

  $ mingw32-make.exe mingw

Tested with mingw-get-inst-20120426.exe and updated around 2013-04-15.