Mirror of #277 requested by the contribution requirement. I am sorry for having this issue late.

Fixes # N/A
Proposed changes: Replace isinff(...) with a combination of isinf(...) and signbit(...)
Benchmark results: No changes in performance.
Test suite changes: N/A
Almost the same to #188, but more aggressive. isinff(...) is completely remove from the source tree.
Reason: Mentioned in PR188, isinff(...) is both obsolete and non-standard. To maximize portability and suggested by GNU, we should have it replaced.
PS, Sorry due to our process we need to always fork under tags even if a tag only contains version changes. I have a rebased branch ready for merge now.

Test failed:

box(empty).center() to be in (0, 0, 0) FAIL

The test fails because isinff(...) is used; it is non-standard and obsolete (by GNU), it has different behaviors on QNX compared to Linux.