Issue #20079: Added locales supported in glibc 2.18 to locale alias table.

The makelocalealias.py script now can parse the SUPPORTED file
from glibc sources and supports command line options for source paths.
diff --git a/Tools/i18n/makelocalealias.py b/Tools/i18n/makelocalealias.py
index 10887ce..ca69daa 100755
--- a/Tools/i18n/makelocalealias.py
+++ b/Tools/i18n/makelocalealias.py
@@ -8,6 +8,7 @@
 """
 import locale
 import sys
+_locale = locale
 
 # Location of the alias file
 LOCALE_ALIAS = '/usr/share/X11/locale/locale.alias'
@@ -51,6 +52,37 @@
         data[locale] = alias
     return data
 
+def parse_glibc_supported(filename):
+
+    with open(filename, encoding='latin1') as f:
+        lines = list(f)
+    data = {}
+    for line in lines:
+        line = line.strip()
+        if not line:
+            continue
+        if line[:1] == '#':
+            continue
+        if '/' not in line:
+            continue
+        line = line.rstrip('\\').rstrip()
+        alias, _, alias_encoding = line.partition('/')
+        # Lower-case locale
+        locale = alias.lower()
+        # Normalize encoding, if given
+        if '.' in locale:
+            lang, encoding = locale.split('.')[:2]
+            encoding = encoding.replace('-', '')
+            encoding = encoding.replace('_', '')
+            locale = lang + '.' + encoding
+        # Add an encoding to alias
+        alias, _, modifier = alias.partition('@')
+        alias = _locale._replace_encoding(alias, alias_encoding)
+        if modifier and not (modifier == 'euro' and alias_encoding == 'ISO-8859-15'):
+            alias += '@' + modifier
+        data[locale] = alias
+    return data
+
 def pprint(data):
     items = sorted(data.items())
     for k, v in items:
@@ -92,8 +124,19 @@
     return errors
 
 if __name__ == '__main__':
+    import argparse
+    parser = argparse.ArgumentParser()
+    parser.add_argument('--locale-alias', default=LOCALE_ALIAS,
+                        help='location of the X11 alias file '
+                             '(default: %a)' % LOCALE_ALIAS)
+    parser.add_argument('--glibc-supported',
+                        help='location of the glibc SUPPORTED locales file')
+    args = parser.parse_args()
+
     data = locale.locale_alias.copy()
-    data.update(parse(LOCALE_ALIAS))
+    if args.glibc_supported:
+        data.update(parse_glibc_supported(args.glibc_supported))
+    data.update(parse(args.locale_alias))
     data = optimize(data)
     print_differences(data, locale.locale_alias)
     print()