mknative-gcc for GCC 10.5.0.

regen everything for GCC 10.4.0.

mknative-gcc for GCC 10 and almost all platforms. one of the
myriad of arm platforms, and the powerpc* platforms are not
yet done.

mknative-gcc for gcc 9.3.0 and arm64, alpha, hppa, ia64, m68*, mipseb,
powerpc, riscv*, sh3*, sparc*, vax.

move data from README.gcc8 to README.gcc9.

mknative-gcc for all platforms for GCC 8.4.0.

mknative-gcc for GCC 8.3 and all ports.

partial mknative-gcc for gcc7 and riscv. only libgcc-bootstrap works so
far as libgcc-bootstrap actually doesn't work so building real libs fails.

rerun mknative for GCC 4.8.4 and all platforms.

m68000 needs -fPIC removed (again), and hppa c++config.h turned off
several things present in -lm, fixed by hand.

regen mknative for gcc 4.8-2014-10-09.

RISC-V configury