v.surf.rst: fix compilation for clang

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@70294 15284696-431f-4ddb-bdfa-cd5b030d7da7

lib/rst/interp_float/segmen2d_parallel.c

@@ -18,7 +18,9 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <math.h>
+#if defined(_OPENMP)
 #include <omp.h>
+#endif
 #include <grass/gis.h>
 #include <grass/glocale.h>
 #include <grass/interpf.h>

vector/v.surf.rst/main.c

@@ -22,7 +22,9 @@
  *
  *****************************************************************************/
 
+#if defined(_OPENMP)
 #include <omp.h>
+#endif
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>