Some modules are written such that they can be included
or excluded at runtime. These are added to the OPTMODULES
list in the makefile for a given board.
This change provides a mechanism to allow a build to force
a given module to be built-in (ie. always initialized)
regardless of the configuration in hwsettings.
The main use case for this is to handle a module being optional
on one platform but essential on another.
All modules added to the MODULES list in the Makefile will
automatically result in a matching #define in the form
MODULE_TheModuleName_BUILTIN
being defined in the CFLAGS for all compiled source.
Note that the capitalization of TheModuleName must match
exactly the capitalization used in the MODULES list.
