Broken examples.

[QuLogic]

I'm trying to test all examples, but some either have no instructions, or do not work:

• acoustic_poroelastic: Solver fails with message STOP pressure calculation not implemented for poroelastic media yet, you should compute sigma_yy here. No mention of this in the README.
• anisotropic_zinc_crystal: No instructions. However, it appears to work okay by copying all files to the DATA directory.
• CPML_absorbing_layers: Instructions are vague, I assume this needs the Gmsh mesher.
• global_Earth_ak135f: No instructions. I compiled the Fortran file in that directory, ran it, and copied everything to a DATA directory. However, the mesher fails with the message: No match in parameter file for keyword 'solver.use_existing_STATIONS'
• initial_plane_wave: Solver fails with STOP error: at least one source has x < xmin of the mesh.
• Rayleigh_wave_no_crack: Mesher fails with message: STOP need STACEY_ABSORBING_CONDITIONS set to .true. in order to use add_Bielak_conditions
• salt_dome_CUBIT_mesh/CPML_homogeneous: Solver crashes:

Program received signal SIGFPE: Floating-point exception - erroneous arithmetic operation.

Backtrace for this error:
#0  0x34B8A194F7
#1  0x34B8A19B3E
#2  0x349B035CCF
#3  0x42086D in compute_forces_viscoelastic_
#4  0x4924A3 in MAIN__ at specfem2D.F90:?

• salt_dome_CUBIT_mesh/CPML_normal_fluid_solid: Solver fails with message: STOP PML do not support the fluid-solid boundary not inside CPML_X_ONLY
• Tape2007_kernel: Solver fails with message: cannot draw a SH scalar field as a vector plot, turn PostScript plots off

A lot of the process.sh files run make. I'm not sure why, as the READMEs all say to compile first.

[komatits]

created a new directory called "currently_broken_or_obsolete_examples_but_do_not_remove" and moved the broken examples there, with a new file called HERE_IS_THE_REASON_WHY_THIS_EXAMPLE_IS_BROKEN.txt explaining why/how they are broken.
I will try to fix all the other examples.

[komatits]

fixed all the remaining broken examples