Add test for vc-relax with vdw MBD

test-suite/pw_vdw/vdw-mbd-vc-relax.in

@@ -0,0 +1,37 @@
+ &CONTROL
+   calculation =   "vc-relax"
+ /
+ &SYSTEM
+   ibrav = 0 ,
+   A = 3.70971016 ,
+                         nat  =  2 , 
+                        ntyp  =  1 , 
+                     ecutwfc  =  25.0 ,
+                        nbnd  =  9 , 
+                 occupations  =  'smearing' ,
+                    smearing  =  'mp' ,
+                     degauss  =  0.005
+                     vdw_corr = 'mbd'
+                     input_dft = 'PBE' ! pseudo is PZ, need to hardcode here
+ /
+ &ELECTRONS
+                    conv_thr  =  1.0d-7 
+ /
+ &IONS
+   ion_dynamics = 'bfgs' ,
+ /
+ &CELL
+   cell_dynamics = 'bfgs' ,
+   press = 500.00
+ /
+CELL_PARAMETERS alat 
+    0.58012956  0.00000000  0.81452422
+   -0.29006459  0.50240689  0.81452422
+   -0.29006459 -0.50240689  0.81452422
+ATOMIC_SPECIES
+   As   74.90000  As.pz-bhs.UPF
+ATOMIC_POSITIONS crystal 
+As    0.290010       0.290010       0.290010
+As   -0.290010      -0.290010      -0.290010
+K_POINTS automatic 
+  4 4 4   1 1 1