Charlie Jacobsen authored Sep 05, 2015 and Vikram Narayanan committed Oct 25, 2016

This is a boring but important commit that we need for
our glue code example (that is still in progress).

The main motiviation is: One kLCD (like a booting kLCD) may
want to create other threads to run kernel modules, and it
may want to grant them capabilities to resources. (Before
this, this wasn't possible - all kLCDs were isolated from
each other.) Another alternative (possibly better) for the
future is to allow threads to share cspaces. But we're
probably not there yet.

Adds the following to the kLIBLCD interface:

-- klcd_create_klcd - essentially creates another kernel
   thread and initializes the lcd-specific stuff like its
   cspace; the creator can then use lcd_cap_grant to grant
   this thread capabilities

-- klcd_create_module_klcd - creates a klcd (using
   klcd_create_klcd) and loads a kernel module for the klcd
   to run

-- klcd_destroy_module_klcd - destroys klcd (the kernel
   thread, etc.) and unloads the module

Adds test and an example group of modules that show how to use
this.