Simplify Python checks in configure.ac

Simplify Python checks in configure.ac

The version checking code is not necessary. It is only used to define
HAVE_LIBPYTHON2_6 or HAVE_LIBPYTHON2_7, which is not used anywhere.

If a version check is desired, the PY_{MAJOR,MINOR}_VERSION macro from
the Python headers can be (and is) used, which does not require updating
configure.ac whenever a new Python version is released.

gdb/ChangeLog:

2019-10-24  Christian Biesinger  <cbiesinger@google.com>

	* config.in: Regenerate.
	* configure: Regenerate.
	* configure.ac: Remove the code that uses sed to get the python
	version and defines HAVE_LIBPYTHON2_6 / HAVE_LIBPYTHON2_7.

Change-Id: I07073870d9040c2bc8519882c8b3c1368edd4513