msh4 io dosen't work for the fine mesh case

[yangbai90]

The msh4 file generated by examples/pffracture/logo.geo can not be well recognized once the mesh is extremely fine(msh file size>=15Mb), the following error can be captured:

******************************************************************************
*** Error:i=0 is out of range(256876) for your vector                  !!! ***
******************************************************************************
******************************************************************************
*** AsFem exit due to some errors                                      !!! ***
******************************************************************************

However, the same geo file can produce the working msh2 file for the simulation. Moreover, this issue can be resolved in msh4 importor when the mesh is coarse (~10k nodes). The check should be executed for:

• [x] msh4 io for large mesh case
• [x] gmsh's msh4 output function for extremely fine mesh

[yangbai90]

In particular for the fine mesh case, the new version of gmsh will generate more nodes than the actual one utilized in the elemental connectivity vector. Now this issue has been resolved in c3972d5d3b8d5abb53a725db44941e2af0108edb