[PR/24474] Add gdb.lookup_static_symbol to the python API

[PR/24474] Add gdb.lookup_static_symbol to the python API

Similar to lookup_global_symbol, except that it checks the
STATIC_SCOPE.

gdb/ChangeLog:

2019-07-30  Christian Biesinger  <cbiesinger@google.com>

	PR/24474: Add a function to lookup static variables.
	* NEWS: Mention this new function.
	* python/py-symbol.c (gdbpy_lookup_static_symbol): New function.
	* python/python-internal.h (gdbpy_lookup_static_symbol): New function.
	* python/python.c (python_GdbMethods): Add new function.

gdb/doc/ChangeLog:

2019-07-30  Christian Biesinger  <cbiesinger@google.com>

	* python.texi (Symbols In Python): Document new function
	gdb.lookup_static_symbol.

gdb/testsuite/ChangeLog:

2019-07-30  Christian Biesinger  <cbiesinger@google.com>

	* gdb.python/py-symbol.c: Add a static variable and one in an anonymous
	namespace.
	* gdb.python/py-symbol.exp: Test gdb.lookup_static_symbol.