latest emscripten -O2 support

These changes allow the latest build of emscripten (2013 August 15)
to build MESS with -O2, making Coleco and Canon Cat basically
usable in Chrome.
Additional -O2 options for inlining large functions
after profiling by azakai
bump emscripten to latest master per @vitorio in #17
Added ZX Spectrum makefiles
Added MSX makefiles