Make sure all symbols are defined and use #if to check math symbol availability
Make math library an extension module to make windows happy
Port over portable copysign
Silence llvmpy debug output in tests
Update some tests to handle the absence of clang, long double and long long
Make sure windows can find the math shared library
Disable building shared library with clang for now (rely on setup.py)
Add portability header for exporting symbols
Export symbols with DL_EXPORT
Adapt npy_math.h with export declarations