testcrypt.h: invent FUNC_WRAPPED.

FUNC_WRAPPED is an alternative keyword to FUNC which you can use to
introduce a function specification in testcrypt.h, indicating that the
function is _not_ the one of the same name used in the main PuTTY
code, but instead a wrapper on it in testcrypt.c whose API was
reworked to be more friendly to translation into Python.

There are a lot of those wrappers already, and previously they passed
without comment in testcrypt.h, and were put into service by #defining
over the top of each name before expanding the marshalling functions.
Now, all those #defines are gone, because the use of FUNC_WRAPPED in
testcrypt.h is enough to clue in the marshalling wrapper to be
generated with a call to foo_wrapper() instead of foo().

Mostly the purpose of this is to make testcrypt.h a bit more
self-documenting: if you see FUNC_WRAPPED, you know not to be confused
by the Python and C function definitions totally failing to match.

test/testcrypt.py

@@ -327,7 +327,8 @@ def _parse_testcrypt_header(tokens):
         return tok
 
     while True:
-        tok = expect("FUNC", "at start of function specification", eof_ok=True)
+        tok = expect({"FUNC", "FUNC_WRAPPED"},
+                     "at start of function specification", eof_ok=True)
         if tok is None:
             break