Fixed LuaJIT native build on Raspberry Pi.

Only set the assembler flag to either -m32 or -m64 when the target architecture is X64.
If all font's glyph do not fit into one page, begin filling texture pages dynamically as glyphs are used.
Code cleanup.
Fixed LuaJIT native build on Raspberry Pi.

Missed out one more condition check before applying -m32/64 flag.
Adapted Aster Jian's mutable glyph mechanism. Globally switchable on from the UI subsystem. Configurable font texture max size in UI subsystem.
Merge branch 'font2'
Filter target architecture information if the tool is available.

The initial target architecture detection for LuaJIT on Raspberry Pi native build was painfully slow due to the amount of output produced by compiler.
The filter reduces the number of output rows and speeds up the process significantly.