lang/python{27,33,34,35,36}: Install GDB debugging script

Users with a GDB that supports [1] Python extensions will automatically
load the extra debugging extensions when debugging programs that are
linked with libpythonX.Y.so.foo.

This enables extensions like 'py-bt' and 'py-frame' as described in
the Fedora Wiki Article: Easier Python Debugging [2], which can be
useful for debugging Python program state from crashes in C extensions,
for example.

[1] PYTHON option enabled in devel/gdb
[2] https://fedoraproject.org/wiki/Features/EasierPythonDebugging

PR: 203021
Submitted by: cem
Reviewed by: mat, koobs (python)
Approved by: koobs (python)
Differential Revision: D10398