Fix closes Issue12529 - cgi.parse_header failure on double quotes and

semicolons. Patch by Ben Darnell and Petri Lehtinen.

Lib/cgi.py

@@ -293,7 +293,7 @@ def _parseparam(s):
     while s[:1] == ';':
         s = s[1:]
         end = s.find(';')
-        while end > 0 and s.count('"', 0, end) % 2:
+        while end > 0 and (s.count('"', 0, end) - s.count('\\"', 0, end)) % 2:
             end = s.find(';', end + 1)
         if end < 0:
             end = len(s)