PR middle-end/19100
	* c-common.c: Include real.h.
	(c_common_truthvalue_conversion): Avoid destructively modifying expr.
	Correctly handle TREE_CONSTANT_OVERFLOW for INTEGER_CST.
	Correctly handle TREE_CONSTANT_OVERFLOW and NaNs for REAL_CST.
	* Makefile.in (c-common.o): Update dependencies.

	* gcc.dg/conv-3.c: New test case.

From-SVN: r92957