Fails to compile with GFortran

[awvwgk]

Seems like recent changes break the support for GCC:

FAILED: gtb.p/source_symmetry.f90.o 
gfortran -Igtb.p -I. -I.. -fdiagnostics-color=always -D_FILE_OFFSET_BITS=64 -Wall -O2 -g -ffree-line-length-none -fbacktrace -fopenmp -Jgtb.p -o gtb.p/source_symmetry.f90.o -c ../source/symmetry.f90
../source/symmetry.f90:44:29:

   44 |       Type (c_ptr) :: csptr                      !C-Compatible Pointer
      |                                        1
Warning: Nonconforming tab character at (1) [-Wtabs]
../source/symmetry.f90:46:28:

   46 |       Integer :: sflen (1)                       !Needed for correct call of c_f_pointer
      |                                        1
Warning: Nonconforming tab character at (1) [-Wtabs]
../source/symmetry.f90:71:21:

   71 |       csptr = c_loc (sfsym)! Get address of dummy string
      |                     1
Error: Argument X at (1) to C_LOC shall have either the POINTER or the TARGET attribute