Updated HACKING to document the new type structures
make check, test target
Pulled out PARSE_BTYPE - corrected mode checking
"register" is valid on parameters

Also made more fatal errors wait until the end of the pass
Argument storage test
Pull out struct/union/enum DWARF output
Moved out_label() declaration
Dwarf subprogram skeleton
Free addr_str
DW_TAG_subprogram types refer to the return type
Store high and low pc in DWARF's translation unit info
DW_AT_decl_{line,file} are shown in variable and subprogram DIEs
Pulled out formal parameter DWARF code, for TAG_subprogram
Inlined dwarf_attr_lbl()
Distinguish between signed and unsigned LEB128s - for negative offsets
Debug information for function-arguments - can be debugged
Link up the .debug_line section to .debug_info

This allows breakpoints to be placed using source line numbers, and
addresses to be resolved back into source lines, etc.
Extend the DWARF high_pc to the end of the final function
Better [SU]LEB128 debug information output
Handle void types in DWARF output - no DW_AT_type emitted