Corrected typos in ad_t3dbc_im.F and read_phypar.F

[arango]

Corrected couple of typos:

• ad_t3dbc_im.F: A line was removed when processing the modifications to the lateral boundary conditions (​src:ticket:519). At line 115, we need to have:

              ad_t(Iend+1,Jend+1,k,nout,itrc)=0.0_r8
  

• read_phypar.F: At line 1434, we need to have instead:

                IF (idVair.eq.0) THEN
  

  Many thanks to Hugo Bastos for ​reporting this typo.

• mod_forces.F: corrected a typo in the module documentation.