Move the definitions of the various GMPLS "struct tok"s out of gmpls.h

Move the definitions of the various GMPLS "struct tok"s out of gmpls.h
into a new gmpls.c file; have gmpls.h contain only external declarations
of those structures.  That removes compiler warnings about static
structures being defined but not used, and also lets more than one file
share structures used in both of those files, rather than having private
definitions of them.