floor, ceiling, etc on exacts [1.6]

[Kevin Ryde]

        * numbers.c (scm_floor, scm_ceiling, scm_truncate_number,
        scm_round_number): New functions, replacing scm_tc7_cxr definitions,
        and ensuring exact arguments give exact results, as required by R5RS.
        Derived in part from the same by Marius in the cvs head.  Reported by
        Ray Lehtiniemi.

        * tests/numbers.test (truncate, round, floor, ceiling): Add tests, in
        particular exercising exactness fixes and scm_round 2^53-1 fix.

These bits and pieces of tests will be for the cvs head too, though
the 2^53-1 part is still broken there at the moment (scm_round_number
is afflicted by the same problem as scm_round was).

numbers.c.floor-exact.diff
Description: Text document

numbers.test.floor-exact.diff
Description: Text document