Enumeration Correction in C-Interface

Following issue #144.
@zdne this is the blueprint that I added, the [previous](https://github.com/alikh31/snowcrash/blob/alikh31/issue%23144/test/test-csnowcrash.cc#L91) blueprint that you mentioned as invalid was the one you told me to copy from @abtris test case, shall I correct that one or having this test is enough and [the other one](https://github.com/alikh31/snowcrash/blob/alikh31/issue%23144/test/test-csnowcrash.cc#L91) should be removed?