System-wide summaries:

 - Summaries for char*, const char* and char[] are loaded at startup as
   system-wide summaries. This means you cannot delete them unless you use
   the -a option to type summary delete/clear
 - You can add your own system-wide summaries by using the -w option to type
   summary add
Several code improvements for the Python summaries feature

llvm-svn: 135326