Fix emscripten config; make dreamtorus work

This fixes up a bit of the emscripten config -- REGAL_SYS_EMSCRIPTEN_STATIC should be off by default, since it requires source changes in code that's using it.

With these changes, dreamtorus works in both configurations; in the default config, the "vvuk-regal" branch of emscripten needs to be used, but the EMSCRIPTEN_STATIC should work currently.  That should be merged into emscripten inbound later today, though.