- add optional ->output() method to struct section
- make output_section() use ->output() if present
- make strtab_init() set up ->output
- change strtab_write() into a trivial wrapper for output_section()
- embed a strtab's associated section in the strtab itself
- change append_section() to enter name before reading dot
- synthesize .shstrtab with append_section(), remove old kludge
remove ->image == NULL test in append_section, output_shdr
don't store dummy value in section_strtab.image or section_shstrtab.image
hoist symtab declaration to output() top-level, don't store it in
section_symtab.image
drop fixmes at assignments to .dot as they are Ok
