Added another "romfs" parameter to SConstruct. It can take one of 3 values:
- "verbatim" (default): copy all the files from the eLua romfs/ directory to the binary image (exactly what happened until now)
- "compress": use LuaSrcDiet (http://luaforge.net/projects/luasrcdiet, now included in the eLua distribution) to "compress" the source code by using different tricks (shorter identifiers, removing comments and EOLS, and so on). The output is still a compilable Lua file (although in most case it looks completely different from the original) which is copied in the eLua binary image instead of the original Lua file. The compression obtained by using this method seems to be very good in practice, thus it will save flash when needed.
- "compile": use the eLua cross compiler (that must be built first by running 'scons -f cross-lua.py') to precompile the Lua files to bytecode, and write the bytecode to the image instead of the source file. This way, one can save both time (the scripts don't need to be compiled anymore) and RAM (for the same reason, especially since the Lua parser uses the stack a lot, which can lead to very nasty and hard to diagnose stack overflow bugs). It will be even more useful in the future, when (hopefully) more and more Lua bytecode data structures will be available directly from Flash (without having to copy them RAM as it happens now). It might also decrease the romfs memory footprint, but then again, it might not; it pretty much depends on the Lua programs included in the romfs.
