Fixed problem of "strdup" not found in mingw-w64

Modified api.c to work with mingw-w64 on windows.
Refined to ensure that redefinition only occurs in Win64 (mingw-w64)
get rid of messages
Added support for Win64 to api.c
Merge pull request #45 from stuartallenmills/master

Patch for Win64 "strdup symbol not found" link problem.