testsuite: fix more dg-* whitespace issues

testsuite: fix more dg-* whitespace issues

A handful of cosmetic ones in here but most meant the directive wasn't
doing anything.

gcc/testsuite/ChangeLog:
	PR target/98743
	PR tree-optimization/105820

	* g++.dg/cpp0x/udlit-namespace-ambiguous.C: Fix whitespace.
	* g++.dg/cpp2a/constexpr-init21.C: Ditto.
	* g++.dg/diagnostic/wrong-tag-1.C: Ditto.
	* g++.dg/init/self1.C: Ditto.
	* g++.dg/opt/pr98743.C: Add missing '}' to terminate dg directive.
	* g++.dg/parse/error8.C: Fix whitespace.
	* g++.dg/template/explicit-args6.C: Add missing '{' to begin dg directive.
	* g++.dg/template/unify9.C: Fix whitespace.
	* g++.dg/tree-ssa/pr105820.C: Ditto.
	* g++.dg/warn/Wmismatched-tags-8.C: Add missing braces.
	* gcc.dg/cpp/cmdlne-dM-M.c: Ditto.
	* gcc.dg/tree-ssa/reassoc-32.c: Ditto.
	* gcc.dg/tree-ssa/reassoc-33.c: Ditto.
	* gcc.dg/tree-ssa/reassoc-34.c: Ditto.
	* gcc.dg/tree-ssa/reassoc-35.c: Ditto.
	* gcc.dg/tree-ssa/reassoc-36.c: Ditto.
	* gcc.dg/tree-ssa/reassoc-39.c: Ditto.
	* gcc.dg/tree-ssa/reassoc-41.c: Ditto.