Redefining term-attrs-[io]speed[-set!] in terms of accessor functions,
cfgetispeed, cfgetospeed, cfsetispeed and cfsetospeed, instead of
non-portable field names.
Checking for __GNU_LIBRARY__ to use random_r.
Improving (chibi doc) docs.
Fixing sexp_context_align_pos when SEXP_USE_ALIGNED_BYTECODE is enabled.
Don't backtrack to remove bytecode if we're in aligned mode.
initstate_r is a glibc extension