uniqtypes: make __uniqtype__void a weak definition.
compilerwrapper: better guesswork about whether we're a link command.
Makefile tweaks
Fix some signed/unsigned warnings.
Tweak symbol visibilities so that linking _preload.a into an executable (node/V8) works as intended.
Move link-used-types scripts from libcrunch.
Don't use malloc, free or getline when processing maps, to avoid initialization problems.
Use fake libunwind by default. Build liballocs_exe.a for linking into executables. Some tweaks to symbol visibility to make executable case work.