Port over changes to the crunch symbol hiding method from NetBSD.

The older symbol hiding method breaks for MIPS. This implements
symbol hiding through renaming to a symbol name which is highly
unlikely to clash.

The NetBSD code didn't use byte-swapping macros for endian-awareness;
so it didn't work when cross-compiling a MIPS world on i386/amd64.
This patch includes those (as best as I could figure what they
should be) and has been tested to generate valid MIPS crunch
binaries both cross- and native- compiled.