Cppcheck has identified a lot of unused functions. This removes funcs that
are unlikely to ever be used. Others that might be useful for debugging I've
commented out with "#if 0".
This narrows the range of Unicode codepoints fish reserves for its own
use from U+E000 thru U+F8FE (6399 codepoints) to U+F600 thru U+F73F (320
codepoints). This is still not ideal since fish shouldn't be using any
Unicode private-use codepoints but it's a step in the right direction.
This partially addresses issue #2684.
This change moves source files into a src/ directory,
and puts object files into an obj/ directory. The Makefile
and xcode project are updated accordingly.
Fixes#1866
