./configure issue

could it please, please print errors if pkgconfig is not available?
it took me half an hour to find out what the problem was, as i didn't know anything of pkgconfig. at the moment, i'm trying to figure out why musepack won't be listed in the "decoder plugins" line printed out at the end of ./configure, although i have libmpcdec installed and configure.log seems to be satisfied about presence and usability of it... and obviously musepack support is activated anyway.

all in all, configure should be a bit more communicative ;)

I've added such warning, thanks.

thanks a lot :-)