ENH: try to improve make speed by getting rid of some implicit rules that were still around.

Source/cmLocalUnixMakefileGenerator3.cxx

@@ -738,6 +738,18 @@ cmLocalUnixMakefileGenerator3
     makefileStream, "Disable implicit rules so canoncical targets will work.",
     ".SUFFIXES", no_depends, no_commands, false);
 
+  // turn off RCS and SCCS automatic stuff from gmake
+  makefileStream << "# Remove some rules from gmake that .SUFFIXES does not remove.\n"
+                 << "# This makes gmake faster as it does not try to run implicit rules\n"
+                 << "# on targets that never exist.\n"
+                 << "%: %,v\n"
+                 << "%: RCS/%,v\n"
+                 << "%: RCS/%\n"
+                 << "%: s.%\n"
+                 << "%: %.w\n"
+                 << "%.c: %.w %.ch\n"
+                 << "%: %.tex\n"
+                 << "%: SCCS/s.%\n\n";
   // Add a fake suffix to keep HP happy.  Must be max 32 chars for SGI make.
   std::vector<std::string> depends;
   depends.push_back(".hpux_make_needs_suffix_list");