configure.in (--enable-checking): Add fold category.

configure.in (--enable-checking): Add fold category.

	* configure.in (--enable-checking): Add fold category.
	(ENABLE_FOLD_CHECKING): Define if requested.
	* configure: Rebuilt.
	* config.in: Rebuilt.
	* doc/install.texi: Document it.
	* fold-const.c: Include md5.h.
	[ENABLE_FOLD_CHECKING] (fold): Define to fold_1.
	[ENABLE_FOLD_CHECKING] (fold, fold_checksum_tree, fold_check_failed,
	print_fold_checksum): New functions.

	* fold-const.c (fold): Never modify argument passed to fold, instead
	change a copy and return it.
	* convert.c (convert_to_integer): Likewise.
testsuite/
	* gcc.c-torture/compile/20030725-1.c: New test.

From-SVN: r69886