math.h fix

[m-mcgowan]

removed extraneous include of math.h in spark_wiring_arduino.h - we only want to include it when Arduino compatibility is enabled (via Arduino.h)

Problem

math.h was being included, plus a check for isnan being a defined symbol. This will fail if <algrithm> has already been included before the header.

Solution

Only include math.h when Arduino compatibility is requested. (math.h was not included in 0.6.0).

Steps to Test

Run the firmware library compile script to validate all libraries that compiled with 0.6.0 continue to compile with this PR. (this has been done.)

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Completeness

• User is totes amazing for contributing!
• Contributor has signed CLA (Info here)
• Problem and Solution clearly stated
• N/A Run unit/integration/application tests on device
• N/A Added documentation
• Added to CHANGELOG.md after merging (add links to docs and issues)

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Bug fix

• [PR #1310] Fixes a error when <algorithm> has already been included before the math.h header. Now we only include math.h when Arduino compatibility is requested. (math.h was not included in 0.6.0).