autoconf likes to have the m4 directory
Now generates and installs a pkg-config .pc file, now you can do the following (at least when installed to --prefix=/usr):
$ gcc src/test.c `pkg-config --libs libpopennoshell` -o test

$ pkg-config --libs libpopennoshell
-lpopennoshell
Merge pull request #2 from falsovsky/pc-file

Generates pkg-config .pc file