Problem:    More functions can be used as methods.
Solution:   Make float functions usable as a method.

Problem:    Some balloon tests don't run when they can.
Solution:   Split GUI balloon tests off into a separate file. (Ozaki Kiichi,
            closes #4538)  Change the feature check into a command for
            consistency.

Problem:    Tests are silently skipped.
Solution:   Throw an exception for skipped tests in more places.

Problem:    Some eval functionality is not covered by tests.
Solution:   Add a few more test cases. (Masato Nishihata, closes #4374)

Problem:    It is not easy to check for infinity.
Solution:   Add isinf(). (Ozaki Kiichi, closes #3787)

Problem:    float2nr() is not exactly right.
Solution:   Make float2nr() more accurate.  Turn test64 into a new style test.
            (Hirohito Higashi, closes #1688)

Problem:    Still some float functionality is not covered by tests.
Solution:   Add more tests. (Dominique Pelle, closes #1364)

Problem:    str2nr() and str2float() do not always work with negative values.
Solution:   Be more flexible about handling signs. (LemonBoy, closes #1332)
            Add more tests.

Problem:    On MS-Windows some float functions return a different value when
            passed unusual values.  strtod() doesn't work for "inf" and "nan".
Solution:   Accept both results.  Fix str2float() for MS-Windows.  Also
            reorder assert function arguments.

Problem:    Several float functions are not covered by tests.
Solution:   Add float tests. (Dominique Pelle)