Fix <unimplemented> for size_t return type on builtins

dstep/translator/Type.d

@@ -300,8 +300,11 @@ do
     if (declaration.isValid)
         return translateType(context, declaration, rewriteIdToObjcObject);
     else
+    {
+        type = type.canonical.isValid ? type.canonical : type;
         return translateType(context, type.kind, rewriteIdToObjcObject)
             .makeSourceNode();
+    }
 }
 
 string translateComplex (Type type)

tests/functional/Tests.d

@@ -227,6 +227,14 @@ unittest
     );
 }
 
+unittest
+{
+    assertRunsDStepCFile(
+        "tests/functional/size_t_redeclared.d",
+        "tests/functional/size_t_redeclared.h"
+    );
+}
+
 // DStep should exit with non-zero status when an input file doesn't exist.
 unittest
 {

tests/functional/size_t_redeclared.d

@@ -0,0 +1,6 @@
+import core.stdc.config;
+
+extern (C):
+
+c_ulong strlen (const(char)* __s);
+c_ulong fread ();

tests/functional/size_t_redeclared.h

@@ -0,0 +1,6 @@
+
+#include  <stdio.h>
+
+size_t strlen(const char *__s);
+size_t fread();
+