When using it, we now set the include path to better find the devel curl
headers, and we check for the socklen_t type since the curl memdebug stuff
needs it.

memory leaks etc.

about it shadowing the function sin()

added prototypes for the strcasecmp() functions

that assume them to be unsigned. Stops compiler warnings.

warnings

support --enable-debug to switch on picky compiler options

and the original ares installed in the same lib dir.

This breaks the API and ABI with the existing ares library. We hereby require
the upcoming c-ares 1.0 for asynch name resolves!