gdb: mknative everyone
- add mipsn64e[bl]
- fix default target to ILP32 for mips64e[bl]
- no significant changes expected for others

gdb: mknative everyone except for m68000

m68000 is broken due to missing gmp (MKGCCCMDS = no).

clang build for everyone is also broken for the same reason.
We must reconsider to handle gmp in src/lib/Makefile.

Add powerpc/ia64