Create a pretty-printer for next-pointer lists.
Create a pretty-printer for stringlists.
Change showargv from a function to a command (easier to use).
Clean up some Python PEP violations. Add support for testing null
pointers and caching gdb.Types.
* .ccls: Remove -std=c99: it disables __attribute__ causing warnings.
* .dir-locals.el: Force the C coding style to "gnu".
* make-gdb.py: Add GDB macros for pretty-printing GNU make structs.
* scripts/copyright-update: Use GNULIB_SRCDIR to find update-copyright.