Extract AwaiterTestHelper from AwaiterTimeoutTest
Add FileDescriptorSetApi test helper class
Make PselectApiStub derive from FileDescriptorSetApi
Add find_if and find_if_not functions
Accept exact max value in FileDescriptorSetFake
Enable to set promise result from current exception
Add file descriptor handling in Awaiter
Merge pull request #93 from magicant/feature/proactor

Add file descriptor handling in Awaiter