mknative-gmp output for GMP 6.2.0.

updates for GMP 6.1.2 and most platforms. run tested on i386, amd64,
sparc sparc64, earm, ofppc and mips64eb. build tested on most.

remove the earm* variants as they're now the same as the arm* on

updates for GMP 6.1.2 and most platforms. run tested on i386, amd64,
sparc sparc64, earm, ofppc and mips64eb. build tested on most.

remove the earm* variants as they're now the same as the arm* ones.

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consolidate the trialdivtab.h generation code.

updates for GMP 5.1.3, and new build files for most platforms.

collect common rules in the shared Makefile, this propagates the .OBJDIR
fix done for i386 last year to all other ports

(re-)generate mknative-gcc files for many platforms.
(re-)generate the gmp files for many platforms.