Adding path-relative-to utility, plus pathname cleanup and tests.
(fork) now kills other threads atommically in the child.  Use
(%fork) to keep other threads running in both parent and child.
Adding setenv/unsetenv.
Adding procedure-arity and procedure-variadic?.
Adding path-strip-leading-parents.
Adding create-directory*.
Adding memoization library.
Patch for better error reporting in numeric tests from Per Bothner.
Updating compose example to force exact result.
Adding set-current-environment! and using it in the pure-Scheme load.
This is necessary if the loaded file uses import.
Replacing exact, inexact opcodes with primitive functions.
Updating tests to allow for some potentially inexact results,
and non-zero-based indexing for reader labels, as reported by
Per Bothner.
Adding memoize-file-loader.
Switching SEXP_USE_SEND_FILE to a whitelist for BSD and Linux,
instead of a blacklist.  Fixes issue #192.
Fixing bug when using -x with a language which doesn't have
interaction-environment.  We need to set this in the underlying
core environment first.  Fixes issue #193.
Exporting regexp-match?.
Default conf parent is #f, not null.
Fixing some bignum length comparisons.
GC-preserving intermediate sexp_fixnum_to_bignum result in sexp_expt.
Patch from Lorenzo.
Documentation clarification on the arguments to sexp_alloc_tagged from Lorenzo.