In Pyston C API, there have new added PyFrame_SetLineNumber and
PyCode_HasFreeVars two APIs. Add these two inlined C functions for
CPython.

PyFrame_SetLineNumber is for get frame line number.
PyCode_HasFreeVars is for check whether PyCodeObject has freevars.

[ @kirr: reworked patch for better structure ]

/reviewed-on !1

There is no valid Public Domain in Europe (the only valid Public Domain
in continental law countries is after 75 years after author's death).

So switch to MIT license, which is one of the most permissive OSI
approved ones.

Thanks @jp for clarifying and reminding about this.

This is the project to collect various CAPI functions unifying
compatibility between various C-based Python implementations.

See

    https://github.com/dropbox/pyston/issues/1230
    https://github.com/dropbox/pyston/issues/1241#issuecomment-224691677
    ...

for idea and rationale