Expose skipDefaultLibCheck as a commandline option

Author: mhegazy

src/compiler/commandLineParser.ts

@@ -103,6 +103,10 @@ module ts {
             name: "noResolve",
             type: "boolean",
         },
+        {
+            name: "skipDefaultLibCheck",
+            type: "boolean",
+        },
         {
             name: "out",
             type: "string",