re PR middle-end/39666 (spurious warning with ranged-switch statements)

	PR middle-end/39666
	* gimplify.c (gimplify_switch_expr): If case labels cover the whole
	range of the type, but default label is missing, add it with one
	of the existing labels instead of adding a new label for it.

	* gcc.dg/pr39666-1.c: New test.
	* gcc.dg/pr39666-2.c: Likewise.
	* g++.dg/warn/Wuninitialized-4.C: Likewise.
	* g++.dg/warn/Wuninitialized-5.C: Likewise.
	* gfortran.dg/pr39666-1.f90: Likewise.
	* gfortran.dg/pr39666-2.f90: Likewise.

From-SVN: r147136