limare: destroy remaining objects in limare_finish

With this hopefully the memleaks are gone.
Someone better check with valgrind or something similar, to make sure...
limare: rename some rgb565 to (more generic) 16 in texture code
limare: slightly modify space filler code (texture code)
limare: cleanup texture_16_swizzle
limare: cleanup texture_32_swizzle
limare: constify some variables (texture code)
limare: introduce texture_16_swizzle_block4

Processes 4 pixels at a time, slightly reducing the loop overhead.
The plan is to use NEON asm to sleep this up a lot more.