Fix #95, add local isnan, isfinite macros

[jphickey]

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Describe the contribution In case the system-provided math.h header does not provide an implementation if isnan or isfinite, use a local workaround.

Fixes #95

Testing performed Build on VxWorks 6.9

Expected behavior changes Build is successful

System(s) tested on VxWorks 6.9

Contributor Info - All information REQUIRED for consideration of pull request Joseph Hickey, Vantage Systems, Inc.