implemented p4est_connectivity_reduce.
added connectivity_reduce tests
fixed a typo
corrected a wrong comment for ghost_is_valid
fixed a typo
In test_conn_reduced chagend char* to const char*.
Added connectivity_is_valid assertion to p4est_connectivity_reduce
Removed unneccessary variable and is_valid test from p4est_connectivity_reduce
Added type casts to p4est_ghost_is_valid
removed unused variable
Merge remote-tracking branch 'johannes/develop' into develop
Replace assertions with checks in read_inp_stream