Added cl_khr_fp16 extension support for test_explicit_s2v from basic (#…

…1713)

* Added cl_khr_fp16 support for test_explicit_s2v from basic (issue #142, basic)

* Cosmetic corrections

* cosmetic fix

* Added correction to distinguish signed and unsigned char types for ARM architecture tests

* Added missing pieces of convertion procedure to support half

* Corrected condition to verify if additional pragma is necessary (issue #142, basic)

* Add NaN check for half to float conversion

* check-format fixes

* Add NaN check for all float types

Use std::isnan for float/double types.

Change-Id: I005bddccaa3f8490ac59b2aa431ed315733ad143

* Fix Ubuntu build error with isnan macro definition

Change-Id: I671ed826a9631fbbc66d0aa9b674ab00124c7967

* Check format fixes

* NAN define not needed anymore

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Co-authored-by: Vasu Penugonda <vpenugon@qti.qualcomm.com>
Co-authored-by: Sreelakshmi Haridas <sharidas@quicinc.com>