Update symbol domain and location values for Python

Update symbol domain and location values for Python

In the distant past, there was no distinction between domain_enum and
search_domain.  At that point, there were two sets of enumerators in a
single enum -- which is why these were eventually split.  This
confusion leaked out to the Python API as well, as noted in
PR python/21765.

This patch deprecates the constants that aren't useful to the Python
API.  They are left in place for now, but removed from the
documentation.  Also, their values are changed so that, if used, they
might work.  Finally, missing domains and location constants are
added.

gdb/ChangeLog
2018-10-06  Tom Tromey  <tom@tromey.com>

	PR python/21765:
	* python/py-symbol.c (gdbpy_initialize_symbols): Redefine
	SYMBOL_VARIABLES_DOMAIN, SYMBOL_FUNCTIONS_DOMAIN,
	SYMBOL_TYPES_DOMAIN.  Define SYMBOL_MODULE_DOMAIN,
	SYMBOL_COMMON_BLOCK_DOMAIN, SYMBOL_LOC_COMMON_BLOCK.

gdb/doc/ChangeLog
2018-10-06  Tom Tromey  <tom@tromey.com>

	PR python/21765:
	* python.texi (Symbols In Python): Document the module and
	common-block domains.  Remove documentation for incorrect
	domains.