Fix templated constructors regression

Templated constructors were incorrectly ignored because SWIG thought they were
methods without a return type.
Regression introduced in swig-3.0.0
Closes #245.
Add PEP8_FLAGS variable to the test suite Python makefile.

Put pep8 options into this variable to avoid repeating them twice.

No real changes.
Ignore E402 (import not on top of file) PEP8 error.

Travis uses the latest pep8 sources from Git and since

https://github.com/jcrocholl/pep8/commit/f3a12babd4278f8f7a529a9d1d63d56faf071cf8

this error is given for all Python files generated by SWIG with -builtin
option.
Merge pull request #276 from vadz/pep8

Ignore another pep8 error.
Partial support for %constant and structs

Test case is slightly modified from the test case in issue #250

Use of constant objects does not seem to work in Python - the type is
SwigPyObject instead of constant_directive.Type1.
fixed python global object constants

Fix for Python and -builtin
Fix from Github issue #250
Improve Python builtin and %constant structs

Tweak to previous commit from issue #250 for C compatibility.
Set self to zero too.
Add in missing constant_directive.i test
Add testcase for nested inner class deriving from a templated base class and defined outside of the outer class.

For languages that don't support nested class support, use flatnested.
See issue #270
Merge branch 'master' of github.com:/swig/swig into travis-osx

* 'master' of github.com:/swig/swig:
  Add testcase for nested inner class deriving from a templated base class and defined outside of the outer class.
  Add in missing constant_directive.i test
  Improve Python builtin and %constant structs
  fixed python global object constants
  Partial support for %constant and structs
  Ignore E402 (import not on top of file) PEP8 error.
  Add PEP8_FLAGS variable to the test suite Python makefile.
  Fix templated constructors regression
Fix use of preprocessor null directive

This was broken recently in commit 255c929c5636f54c16261bd92b8eea2005d61b11
for issue #217
Merge branch 'master' into travis-osx

* master:
  Fix use of preprocessor null directive