Allow out-of-tree builds.
Allow out-of-tree builds for 'tests' directory also
Add Makefile.am. Remove some generated files from repository
rtmidi can now easily be nested into another project
Add libtool support (allows ./configure --enable-shared and --enable-static)
Merge pull request #22 from Ace17/master

Autotooling: allow out-of-tree builds.
Memory leak fix in CoreMidi and addition of UserData pointer to error callback.
Merge autotools-patchset and Core memory leak patch into portdescriptor-api