Fix function signature casts in PyMethodDef structs that lead to warnings in gcc-8 (and actually make use of the warnings in gcc-8).

Added more info on pyximport in compilation.rst

Added tests for cdef_classes.rst. Part 3.

Adding tests for "pure python mode" part 5

Adding test for "language basics" part 1

Adding tests for "working with python arrays" part 5

Adding tests for "working with python arrays" part 4

Adding tests for "working with python arrays" part 3

Adding tests for "working with python arrays" part 2

Added tests to "profiling tutorial" part 1.

Added tests for "memory allocation" Part 2

Added tests for cdef_classes.rst. Part 5

Moved the third code snippet from "working with python arrays" into the examples directory for testing.

Added test of a piece of code in "working with python arrays".

Adding tests for "pure python mode" part 7

Adding tests for "pure python mode" part 6

Adding tests for "pure python mode" part 4

Adding tests for "pure python mode" part 3

Adding tests for "pure python mode" part 2

Adding tests for "pure python mode" part 1

Added tests for cdef_classes.rst. Part 4.

Added tests for cdef_classes.rst. Part 2.

Added tests for cdef_classes.rst.

Added tests for some of the code snippets in "calling C libraries"