Fix 32 and 64 bit sizes in Emscripten build.

When configuring with Emscripten, native binaries are run and
the build system's sizes are detected. On a 64 bit system, they
are wrong, causing problems. Emscripten and/or Autoconf would
need to be changed for a proper cross-compile configure, so
this kludge is used instead.
Simplify Emscripten main loop changes and increase speed.

Upon further examination, the added while(1) loop break is
unnecessary because ticksRemain will take care of that.