This removes the USE_PYTHON depdendency for lang/python27 to allow
bsd.python.mk to be transformed into a Uses file without any additional glue
code in Mk/
Additionally, the static/shared build has been replaced by the build process
used for lang/python34, which greatly simplifies the build.
Other changes include:
- Removal of PTH option (ports/191888)
- Removal of bin/smtpd - it's inconsistent with the rest
- Removal of FPECTL option - it's inconsistent with the rest
- New DEBUG option
- Backport of a distutils.build_scripts.copy_scripts() return value for copying scripts with a major.minor version on installation