Remove vacuous states in base64_sem?.c

Move backend names into src/benchmark.c

I don't think these actually affect correctness since there's no way for
0x40 or 0x60 to show up in a parse tree anyway, but they're confusing.

It's causing unreferenced-variable warnings, and isn't referenced
anywhere aside from benchmark.c. If client code is likely to reference
it, perhaps move it into another header, so people who include hammer.h
don't have to refer to it to have warning-free code.

Mention user guide in README

Scons now doesn't throw away PKG_CONFIG_PATH, so NixOS can build it

Scons now doesn't throw away /home/stewart/.nix-profile/lib/pkgconfig:/nix/var/nix/profiles/default/lib/pkgconfig:/run/current-system/sw/lib/pkgconfig, so NixOS can build it

add h_permutation

h_put_value and h_get_value done.

change pointer type to uintptr_t for portability

implement h_with_endianness combinator

Added NetBSD and OpenBSD ports

Make HHashTable resizeable and improve benchmarking output

Ported to OpenBSD.

Make build work on NetBSD

NetBSD's character class test macros are defined such that they produce
a compiler warning when given a char argument. Adding a cast to the call
fixes this.

CLOCK_THREAD_CPUTIME_ID is a linux-specific timer. On NetBSD, the best
way to get timer information appears to be getrusage, which happens to
be fairly cross-platform.

Made mono tool only get loaded when the dotnet bindings are getting built