symbol table changes

symbol table changes

	* add gotype string to symbol table
	* fill in gotype in 6l for known funcs/vars
	* print gotype with nm -t

	* load symbol and pc/ln tables into memory at magic address 0x99<<32.
	* add sys.symdat() to retrieve raw bytes of symbol table
	  and pc/ln table.

most of this should be considered experimental
and subject to change.

R=r
DELTA=157  (128 added, 0 deleted, 29 changed)
OCL=19746
CL=19750