[ #4786 ] if space in the Application path name, system() doesn't work on some platforms

commited temporary fix: executable name is quoted for all platforms except Windows now,
nicely wrapped in #ifdefs. Will be doing nice wrapper function BLI_system for system calls in blenlib
after release.
Please test on all platforms!

source/blender/python/api2_2x/sceneRender.c

@@ -508,8 +508,13 @@ PyObject *RenderData_Play( BPy_RenderData * self )
 		BKE_makepicstring( file, G.scene->r.pic, self->renderContext->sfra, G.scene->r.imtype);
 		if( BLI_exist( file ) ) {
 			calc_renderwin_rectangle(640, 480, G.winpos, pos, size);
+#ifdef WIN32
 			sprintf( str, "%s -a -p %d %d \"%s\"", bprogname,
 				 pos[0], pos[1], file );
+#else
+			sprintf( str, "\"%s\" -a -p %d %d \"%s\"", bprogname,
+				 pos[0], pos[1], file );
+#endif
 			system( str );
 		} else
 			sprintf( "Can't find image: %s", file );