bpo-30455: Generate all token related code and docs from Grammar/Tokens. (GH-10370)

"Include/token.h", "Lib/token.py" (containing now some data moved from
"Lib/tokenize.py") and new files "Parser/token.c" (containing the code
moved from "Parser/tokenizer.c") and "Doc/library/token-list.inc" (included
in "Doc/library/token.rst") are now generated from "Grammar/Tokens" by
"Tools/scripts/generate_token.py". The script overwrites files only if
needed and can be used on the read-only sources tree.

"Lib/symbol.py" is now generated by "Tools/scripts/generate_symbol_py.py"
instead of been executable itself.

Added new make targets "regen-token" and "regen-symbol" which are now
dependencies of "regen-all".

The documentation contains now strings for operators and punctuation tokens.

Tools/scripts/generate_symbol_py.py

@@ -0,0 +1,53 @@
+#! /usr/bin/env python3
+# This script generates the symbol.py source file.
+
+import sys
+import re
+
+def main(inFileName="Include/graminit.h", outFileName="Lib/symbol.py"):
+    try:
+        fp = open(inFileName)
+    except OSError as err:
+        sys.stderr.write("I/O error: %s\n" % str(err))
+        sys.exit(1)
+    with fp:
+        lines = fp.read().split("\n")
+    prog = re.compile(
+        "#define[ \t][ \t]*([A-Z0-9][A-Z0-9_]*)[ \t][ \t]*([0-9][0-9]*)",
+        re.IGNORECASE)
+    tokens = {}
+    for line in lines:
+        match = prog.match(line)
+        if match:
+            name, val = match.group(1, 2)
+            val = int(val)
+            tokens[val] = name          # reverse so we can sort them...
+    keys = sorted(tokens.keys())
+    # load the output skeleton from the target:
+    try:
+        fp = open(outFileName)
+    except OSError as err:
+        sys.stderr.write("I/O error: %s\n" % str(err))
+        sys.exit(2)
+    with fp:
+        format = fp.read().split("\n")
+    try:
+        start = format.index("#--start constants--") + 1
+        end = format.index("#--end constants--")
+    except ValueError:
+        sys.stderr.write("target does not contain format markers")
+        sys.exit(3)
+    lines = []
+    for val in keys:
+        lines.append("%s = %d" % (tokens[val], val))
+    format[start:end] = lines
+    try:
+        fp = open(outFileName, 'w')
+    except OSError as err:
+        sys.stderr.write("I/O error: %s\n" % str(err))
+        sys.exit(4)
+    with fp:
+        fp.write("\n".join(format))
+
+if __name__ == '__main__':
+    main(*sys.argv[1:])