Win32 only.

this patch makes iconv_getpath() look at the exe/ddl location first
for the charset libraries on Win32.

If it doesn't find an iconv folder there, it tries to use APR_ICONV_PATH
like before.

This way I can make sure that my program uses "my" iconv libs if i think
this is necessary without manipulation of APR_ICONV_PATH. Or i can use
those in APR_ICONV_PATH by not providing private iconv libs.
