Remove some unused buildsym functions

Remove some unused buildsym functions

Now that the DWARF reader uses the builder-based API, we can remove a
few "legacy" functions that were only ever called by it.

gdb/ChangeLog
2018-07-20  Tom Tromey  <tom@tromey.com>

	* buildsym-legacy.h (augment_type_symtab): Don't declare.
	(end_expandable_symtab): Likewise.
	(end_symtab_get_static_block): Likewise.
	(end_symtab_from_static_block): Likewise.
	* buildsym-legacy.c (augment_type_symtab): Remove.
	(end_expandable_symtab): Remove.
	(end_symtab_get_static_block): Remove.
	(end_symtab_from_static_block): Remove.