[NEW] lang/tauthon: Backwards-compatible fork of Python 2.7 interpreter with Python 3.x features

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Note this is not fully connected yet, and needs further changes to integrate
with flavors, addition to Mk/Uses/python.mk (or some equivalent USES=tauthon)
that may need discussion first, for instance, on the package name prefix.

This is committed to serve as a common test bed and for experimentation.
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Maintainer:	olce.freebsd.ports@certner.fr (Olivier Certner)

Tauthon is a backward-compatible fork of Python's 2.7.18 interpreter with new
syntax, builtins, and libraries backported from Python 3.x.

Python code and C-extensions targeting Python 2.7 or below are expected to run
unmodified on Tauthon and produce the same output. But with Tauthon, that code
can now use some of the new features from Python 3.x.

This is not an official Python release. Because of its new features, while
preserving 2.7 compatibility, Tauthon reports 2.8 as its major/minor versions.

Non-exhaustive list of new features:
- Function Annotations
- Keyword-Only Arguments
- "async" and "await" Syntax
- Argument-less "super"
- New Metaclass Syntax
- "nonlocal"
- "yield from" Syntax
- "concurrent.futures" Module
- UTF-8 as the default source encoding

WWW: https://github.com/naftaliharris/tauthon

(Committed with minor changes over submission, particularly a few reorderings
in Makefile to appease portlint -CA.)

PR:		251019
Submitted by:	Olivier Certner (maintainer)

1 files changed, 21 insertions, 0 deletions

diff --git a/lang/tauthon/files/patch-Misc_python-config.in b/lang/tauthon/files/patch-Misc_python-config.in
new file mode 100644
index 000000000000..3390fc6ded9b
--- /dev/null
+++ b/lang/tauthon/files/patch-Misc_python-config.in
@@ -0,0 +1,21 @@
+# pythonx.y-config --ldflags out of /usr and missing -L<install_lib_dir>
+# https://bugs.python.org/issue7352
+
+--- Misc/python-config.in.orig	2015-10-18 07:24:01 UTC
++++ Misc/python-config.in
+@@ -21,6 +21,7 @@ except getopt.error:
+ if not opts:
+     exit_with_usage()
+ 
++libdir = sysconfig.EXEC_PREFIX + '/lib'
+ pyver = sysconfig.get_config_var('VERSION')
+ getvar = sysconfig.get_config_var
+ 
+@@ -50,6 +51,7 @@ for opt in opt_flags:
+         # add the prefix/lib/pythonX.Y/config dir, but only if there is no
+         # shared library in prefix/lib/.
+         if opt == '--ldflags':
++            libs.insert(0, '-L' + libdir)
+             if not getvar('Py_ENABLE_SHARED'):
+                 libs.insert(0, '-L' + getvar('LIBPL'))
+             if not getvar('PYTHONFRAMEWORK'):