tests: Port gen-casefold-txt.pl and gen-casemap-txt.pl to Python 3. See #1332

I've tried to keep the code structure roughly the same.

tests/gen-casefold-txt.py

@@ -0,0 +1,78 @@
+#!/usr/bin/env python3
+# Copyright (C) 1998, 1999 Tom Tromey
+# Copyright (C) 2001 Red Hat Software
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2, or (at your option)
+# any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, see <http://www.gnu.org/licenses/>.
+
+"""
+gen-casefold-txt.py - Generate test cases for casefolding from Unicode data.
+See http://www.unicode.org/Public/UNIDATA/UnicodeCharacterDatabase.html
+Usage:
+    I consider the output of this program to be unrestricted.
+    Use it as you will.
+"""
+
+import sys
+import argparse
+
+
+def main(argv):
+    parser = argparse.ArgumentParser(
+        description="Generate test cases for casefolding from Unicode data")
+    parser.add_argument("UNICODE-VERSION")
+    parser.add_argument("CaseFolding.txt")
+    args = parser.parse_args(argv[1:])
+    version = getattr(args, "UNICODE-VERSION")
+    filename = getattr(args, "CaseFolding.txt")
+
+    print("""\
+# Test cases generated from Unicode {} data
+# by gen-casefold-txt.py. Do not edit.
+#
+# Some special hand crafted tests
+#
+AaBbCc@@\taabbcc@@
+#
+# Now the automatic tests
+#""".format(version))
+
+    # Names of fields in the CaseFolding table
+    CODE, STATUS, MAPPING = range(3)
+
+    with open(filename, encoding="utf-8") as fileobj:
+        for line in fileobj:
+            # strip comments and skip empty lines
+            line = line.split("#", 1)[0].strip()
+            if not line:
+                continue
+
+            fields = [f.strip() for f in line.split(";", 3)[:3]]
+            if len(fields) != 3:
+                raise SystemExit(
+                    "Entry for %s has wrong number of fields (%d)" % (
+                        fields[CODE], len(fields)))
+
+            status = fields[STATUS]
+            # skip simple and Turkic mappings
+            if status in "ST":
+                continue
+
+            code = chr(int(fields[CODE], 16))
+            values = "".join(
+                [chr(int(v, 16)) for v in fields[MAPPING].split()])
+            print("{}\t{}".format(code, values))
+
+
+if __name__ == "__main__":
+    sys.exit(main(sys.argv))