Fix spelling suggestions for reserved words (PR c++/80177)

Fix spelling suggestions for reserved words (PR c++/80177)

gcc/cp/ChangeLog:
	PR c++/80177
	* name-lookup.c (suggest_alternative_in_explicit_scope): Convert
	candidate type of bm from tree to const char *.
	(consider_binding_level): Likewise.
	(lookup_name_fuzzy): Likewise, using this to merge the best
	result from the preprocessor into bm, rather than immediately
	returning, so that better matches from reserved words can "win".
	Guard the rejection of keywords that don't start decl-specifiers
	so it only happens for FUZZY_LOOKUP_TYPENAME.

gcc/testsuite/ChangeLog:
	PR c++/80177
	* g++.dg/spellcheck-pr80177.C: New test case.

From-SVN: r247233