Add highlight of classes

This gives a highlight to variables that are UpperCamelCase, e.g. Python
classes.

syntax/python.vim

@@ -193,6 +193,12 @@ if !s:Enabled("g:python_highlight_file_headers_as_comments")
 endif
 syn keyword pythonTodo		TODO FIXME XXX contained
 
+"
+" Classes
+"
+
+syn match pythonClass       "\(import \)\@<!\<[A-Z][a-zA-Z]*" display
+
 "
 " Errors
 "
@@ -486,6 +492,7 @@ if version >= 508 || !exists("did_python_syn_inits")
   HiLink pythonRepeat           Repeat
   HiLink pythonException        Exception
   HiLink pythonOperator         Operator
+  HiLink pythonClass            Type
 
   HiLink pythonDecorator        Define
   HiLink pythonDottedName       Function