Release v0.2.1

• Remove unnecessary exit() calls from librz/
• Fix wrong demangling of __TIFFSwab16BitData
• Prevent infinite recursion in DWARF parsing
• Detect presence of extern char **environ (fixes old MacOS build)
• Fix SDB and SPP linking with RzUtil
• Fix RzDiff/RzTest to use subprocess API
• Fetching all references with rz-pm to support release tags
• Fix FreeBSD 13 build
• Fix Gentoo SDB build to use proper Python environment
• Fix the wrong use of wcstombs()
• Various UAF, OOB, NULL DEREF fixes