Introduce -strictNullChecks compiler option

src/compiler/commandLineParser.ts

@@ -326,6 +326,11 @@ namespace ts {
             name: "noImplicitUseStrict",
             type: "boolean",
             description: Diagnostics.Do_not_emit_use_strict_directives_in_module_output
+        },
+        {
+            name: "strictNullChecks",
+            type: "boolean",
+            description: Diagnostics.Enable_strict_null_checks
         }
     ];
 

src/compiler/diagnosticMessages.json

@@ -2576,6 +2576,10 @@
         "category": "Message",
         "code": 6112
     },
+    "Enable strict null checks.": {
+        "category": "Message",
+        "code": 6113
+    },
 
     "Variable '{0}' implicitly has an '{1}' type.": {
         "category": "Error",

src/compiler/types.ts

@@ -2420,6 +2420,7 @@ namespace ts {
         allowSyntheticDefaultImports?: boolean;
         allowJs?: boolean;
         noImplicitUseStrict?: boolean;
+        strictNullChecks?: boolean;
         /* @internal */ stripInternal?: boolean;
 
         // Skip checking lib.d.ts to help speed up tests.