Support mixing cython.compile with directive decorators.

[robertwb]

e.g.

import cython

@cython.compile
@cython.boundscheck(False)
def foo():
    ...

Depend on http://trac.cython.org/ticket/737 (#1292)

Migrated from http://trac.cython.org/ticket/738

[robertwb]

@robertwb changed component from Code Generation to Pure Python Mode
commented

[h5rdly]

@robertwb Do you have knowledge of which pure mode decorators do mix with @compile?
@returns, @nogil, @locals and @cfunc are of particular interest.

Thanks

[scoder]

@h5rdly it would be nice if you could try out the relevant ones and provide a list in this ticket, so that we can see what exactly is there or isn't.