Simpler & idempotent setup/installation/uninstallation
Factor SAP arithmetic into bignum-data-sap
No return value for install/uninstall
Whitespace
Bugfix: don't negate-in-place in rational arithmetic
Give more type information to the compiler

 and avoid some spurious notes
Misc. bugfixen, and no more note muffling
Switch to SB-RT, and refactor a lot of stuff
rename to sb-gmp-tests, like other contribs
Avoid polluting the global namespace in system definition, and add a test-op
Test for GMP5.1 at load-time, not compile-time
Make things reloadable
Expose packageful features