Change minimal_symbol inheritance

Change minimal_symbol inheritance

This changes struct minimal_symbol to inherit from general_symbol_info
and updates various macros to cope.

Because MSYMBOL_SET_LANGUAGE and MSYMBOL_SET_NAMES were only used from
a single spot, this patch removes them in favor of simply inlining
their definitions.  I consider this to be somewhat cleaner, not least
because the "phony polymorphism" provided by such macros is not useful
in practice.

gdb/ChangeLog
2019-03-15  Tom Tromey  <tom@tromey.com>

	* symtab.h (struct minimal_symbol): Derive from
	general_symbol_info.
	(MSYMBOL_VALUE, MSYMBOL_VALUE_RAW_ADDRESS)
	(MSYMBOL_VALUE_ADDRESS, MSYMBOL_VALUE_BYTES)
	(MSYMBOL_BLOCK_VALUE, MSYMBOL_VALUE_CHAIN, MSYMBOL_LANGUAGE)
	(MSYMBOL_SECTION, MSYMBOL_OBJ_SECTION, MSYMBOL_NATURAL_NAME)
	(MSYMBOL_LINKAGE_NAME, MSYMBOL_DEMANGLED_NAME)
	(MSYMBOL_SEARCH_NAME): Update.
	(MSYMBOL_SET_LANGUAGE, MSYMBOL_SET_NAMES): Remove.
	* solib.c (gdb_bfd_lookup_symbol_from_symtab): Don't use memset.
	* minsyms.c (minimal_symbol_reader::record_full): Update.