Using DStep v0.2.3-16-g1308991 compiled on Debian Sid with LDC 1.11.0 and LLVM 6.0, I generated a module for fontconfig.h (version 2.13.0). Sadly:

generated/fontconfig.d(257): Error: undefined identifier INT_MAX
generated/fontconfig.d(576): Error: undefined identifier stat_

I am not sure where the stat_ is creeping in. The generated D is:

FcCache* FcDirCacheLoadFile (const(FcChar8)* cache_file, stat_* file_stat);