Purging local, patched MESS 0.142
Re-adding MAME as a submodule
Updating emscripten to include all recent JSMESS-related patches
Purging old 0.142 makefiles
Re-adding a new JSMESS systems location
Purging 0.142-specific helpers
Adding new helper generator and 0.151 updates
Makefile updates for new locations, other minor changes
More granular -listxml grepping for e.g. abc80
Merge pull request #41 from vitorio/151test4

Update to MESS 0.151