socketpair
Just return op not supported.

See #1060
Merge pull request #1060 from arlolra/socketpair

Socketpair
clean up benchmark args
add sig for glUniformMatrix2fv
add testing for gl in asm2g
add erf dep and testing
support for Runtime.addFunction in asm.js
* Added some semaphore, threads and socket stubs.
* Added OpenAL alSourceRewind stub.
* Throws exceptions in stubs.