.gitignore: add man page in CUDA extension

(cherry picked from commit open-mpi/ompi@c9e91ff)

Author: jsquyres

.gitignore

@@ -234,6 +234,8 @@ ompi/mpiext/example/tests/progress_mpifh
 ompi/mpiext/example/tests/progress_usempi
 ompi/mpiext/example/tests/progress_usempif08
 
+ompi/mpiext/cuda/c/MPIX_Query_cuda_support.3
+
 ompi/tools/mpisync/mpisync
 ompi/tools/mpisync/mpirun_prof
 ompi/tools/mpisync/ompi_timing_post