Libmonkey: fix build and add test for mimetype

I fixed the linking with Jemalloc library (issue #102). The libmonkey shared object is linked statically with Jemalloc, so now all symbols from libjemalloc.a are defined in libmonkey.so, effectively increasing its size.

I fixed the proper use of mimetype red-black trees (issue #101), in order to make the library work. I also added a test for the mklib_mimetype_list function, to be sure that the fix actually works. I made other minor modifications to make possible to use the library test suite from tests/lib.

After doing the modifications, I tested with various options to configure (--enable-shared, --prefix=/path, --malloc-libc, --plugdir=/path). After make && make install, the results were as expected.