Config.linux: Clean up warnings when compiling with clang on Linux. make CC=clang CPP=clang++
GNUmakefile: Version was still .94, bump it to .96
debugger: Try to be more helpful if linux libraries are not installed. Fixes #774.
environment: Call unset-os-env when passed an ``f``. Fixes #794.
core-foundation.strings: faster CF>string.
unix: use byte-vectors here.