Here are a few tips for building on Windows:

1) Create a config.h file that defines out things that defines out all the
   features that your compiler doesn't understand (e.g. inline, restrict).
   It also needs to define the CELT_BUILD macro

2) Define the HAVE_CONFIG_H macro in the project build options (NOT in config.h)

3) If you want things to be a lot easier, just use a compiler that supports
   C99, such as gcc