intprops: avoid evaluation of some expressions This makes EXPR_SIGNED (e) easier to use, as it no longer evaluates the expression E. Formerly, E was required to be free of side effects. * lib/intprops.h (_GL_INT_CONVERT, _GL_INT_NEGATE_CONVERT) (EXPR_SIGNED, TYPE_WIDTH, _GL_INT_MINIMUM, _GL_INT_MAXIMUM) (_GL_SIGNED_INT_MAXIMUM): Do not evaluate the expression arg.