Get rid of gcc-ism.
VC++ support.

* ext/yajl/yajl_ext.c (yajl_found_number, yajl_found_hash_key): get rid of C99ism.
* ext/yajl/yajl_ext.c (rb_yajl_parser_new, rb_yajl_encoder_new): get rid of gcc-ism.
* ext/yajl/yajl_enc.c: include ruby.h for the definitions of isinf() and isnan() of VC++.
merge unak/mswin-support