* Move non-libultra libc functions to src/libc/
* Add explicit nops in delay slots
* Don't rely on CPP expanding undefined macros to 0
* Delete old Makefile rules
* Fix type of memset()
* Some GCC flags improvements
* Move -fno-reorder-blocks -fno-zero-initialized-in-bss to assets only
* Add -fno-PIC since some gcc versions use -fPIC as default
* Enable builtin functions on gcc, with appropriate changes to missing_gcc_functions.c
and ultra64/libc.h
* Move -fno-merge-constants -mno-explicit-relocs -mno-split-addresses to overlays only
as they are only needed there for reloc reasons
* Remove unneeded casts in missing_gcc_functions.c
* Change gcc assets flags handling