Fix gdb.ada/info_addr_mixed_case.exp (PR gdb/22670)

Fix gdb.ada/info_addr_mixed_case.exp (PR gdb/22670)

The comments about mixed case in the testcase are actually a red
herring.  The problem here is that we'd get to
ada_lookup_encoded_symbol with "my_table", which wraps the looked up
name in "<>"s to force a verbatim match, and that in turn disables
wild matching.

Fix this by swapping around the internals of ada_lookup_encoded_symbol
and ada_lookup_symbol, thus avoiding the encoding and
verbatim-wrapping in the ada_lookup_symbol case, the case that starts
with a user-provided lookup name.

Ada encoding is still done of course, in the ada_lookup_name_info
ctor.  This could be also seen as avoiding the double-encoding problem
in a different way.

gdb/ChangeLog:
2018-01-05  Pedro Alves  <palves@redhat.com>

	PR gdb/22670
	* ada-lang.c (ada_lookup_encoded_symbol): Reimplement in terms of
	ada_lookup_symbol.
	(ada_lookup_symbol): Reimplement in terms of
	ada_lookup_symbol_list, bits factored out from
	ada_lookup_encoded_symbol.

gdb/testsuite/ChangeLog:
2018-01-05  Pedro Alves  <palves@redhat.com>

	PR gdb/22670
	* gdb.ada/info_addr_mixed_case.exp: Remove kfail.  Extend test to
	exercise lower case too, and to exercise both full matching and
	wild matching.