Not sure about the refcounting

Using _PyUnicode_Writer might be faster but seems more complicated to implement.

Still doesn't do concatenation of FormattedValueNodes correctly.

Parses f-strings into ExprNodes, but with no support for compiling them. Some
known bugs are marked as TODOs.

make str values in compile time DEF env turn into actually usable Unicode strings when compiling under Python 3

copy over "test_call.py" test from CPython 3.5+ to disable an error test that prevents it from building in Cython

Fix typos.

Conflicts:
	CHANGES.rst

Conflicts:
	CHANGES.rst

revert integer literal suffixing again and instead generate C hex literals if no suffix is used to make the C compiler consider unsigned types for their values (see C standard 6.4.4)

Allow passing more than two -v's to cygdb.

Constants in float.pxd are not integers.

Additions to includes

- append U-suffix only on coercion when the target type is unsigned
- append L/LL-suffix when value looks too large for a smaller constant value type

- append U-suffix only on coercion when the target type is unsigned
- append L/LL-suffix when value looks too large for a smaller constant value type