PR fortran/25458
	* simplify.c (gfc_simplify_ibset, gfc_simplify_not): Add call to
	twos_complement.

	* gfortran.dg/chkbits.f90: New test.


Co-Authored-By: Tobias Schlüter <tobias.schlueter@physik.uni-muenchen.de>

From-SVN: r108720