Increase iterations for xi and eta to 5.

This should produce consistent results when comparing ifort, gfortran
and xlf.
Merge branch 'ak135-consistency' of github.com:QuLogic/specfem3d_globe into devel
"Buildbot ran code beautifier."
updated the comment about increasing the number of iterations from 4 to 5
avoids compiler warnings and adds parameter statement to LDDRK constants; needs a workaround in compute_forces_outer_core_Dev.F90 because of a gfortran OpenMP bug
improves minimum required gpu memory estimate
includes a fall-back option in model interpolation
adds flags in constants.h to suppress mesh stretching for 3D moho/410/660 surfaces
timestep and layers fix for asymmetric 1-chunk simulations
updates interpolation tool by adding separate flags for separating elements on 410/650 and moho discontinuities
updates smoothing routine, adding debugging option; moves and renames interpolate_model_kdtree.f90 to src/shared/search_kdtree.f90
updates smoothing tool using a kd-tree search; updates kd-tree routines; moves heap sorting routines to file src/shared/heap_sort.f90
updates routine recalc_jacobian_gll3D() using debug flag for explicit checks
updates routine lagrange_any() for slightly better performance
updates ADIOS flag usage, adding initialization to routine read_parameter_file()
"Buildbot ran code beautifier."
removed see_also_README_inversion_package_list_of_things_to_do_in_the_SPECFEM3D_package.txt
updated a comment about non-local file systems in all the Par_files
cleaned the Par_files
Adds constants for multiple runs