gfortran.dg/gomp/reduction4.f90: Fix testcase

Fix to 'omp scan' commit 005cff4e

gcc/testsuite/ChangeLog:

	* gfortran.dg/gomp/reduction4.f90: Update scan-trees, add
	lost testcase; move test with FE error to ...
	* gfortran.dg/gomp/reduction5.f90: ... here.