Silence lots of warnings during make

Removes a total of about 400 warnings using gfortran, depending on exactly how you compile the code. I've also not touched anything in utils . I’ve also not removed unused variables that are only commented out.

After this PR, here are the top 10 files in terms of warnings:

1. utils/quadpack.f90: 77

2. dist_fn.fpp: 62

3. theta_grid_params.f90: 55

4. utils/spl.f90: 49

5. gridgen4mod.f90: 45

6. init_g.f90: 32

7. run_parameters.f90: 22

8. test_gs2_diagnostics_new.fpp: 18

9. gs2_diagnostics.fpp: 15

10. kt_grids.f90: 12

Most of the remaining warnings are from -Wcompare-reals, which I've also not fixed. We probably want a function like isclose(a, b) to replace most of the instances of this.

• Remove remaining tab characters

• Pass separate arguments to the out-parameters of init_le_grids

• Silence spurious warning about continuation line

• Silence warning about integer division

• Fix type of bishop_save in ingen_mod::interactive

• Remove some unused functions/variables from geometry

  All related to an unfinished comparison with "Xanthopoulos"

• Remove unused variable from generate_fftw_wisdom

• Remove lots of unused variables and imports

• Silence warnings from genquad if not using it

• Remove remaining tabs

• Remove more unused variables

• Reduce scope of n0_tmp and introduce another temporary

  n0_swap is the correct type to silence warning about conversion

• Silence conversion warning from real to int

• Remove some unused module private variables

• Remove more unused variables

• Remove unused variables from tests

• Remove more unused variables from tests

• Only declare mpierr in test if MPI is being used

• Silence conversion warnings in tests by being explicit about kind