* expression.h (enum exp_code): Added OP_NAME.

	* expression.h (enum exp_code):  Added OP_NAME.
	* expprint.c (print_subexp):  Add OP_NAME support.
	* parse.c (length_of_subexp, prefixify_subexp):  Likewise.
	* scm-lang.c (scm_unpack, in_eval_c, scm_lookup_name):  new function.
	* scm-lang.h:  Declare builtin_type_scm;  other minor tweaks.
	* values.c (unpack_long):  If type is SCM, call scm_unpack.
	* scm-valprint.c (scm_val_print):  Use extract_signed_integer,
	instead unpack_long
	* scm-lang.c: More Scheme expression parsing from here ...
	* scm-exp.c:  ... to here.  New file.
	Also, provide for gdb to evaluate simple constants and names..
	* Makefile.in:  Note new scm-exp.{c,o}.