Fixed check for conflicting extern vs no-linkage/static declarations in functions.

test/err/bug2162-static-static-extern.c

@@ -0,0 +1,10 @@
+/* Bug #2162 - conflicting declarations in functions */
+
+static int i;
+
+int main(void)
+{
+    static int i = 42; /* OK - this shadows the i in file scope */
+    extern int i;      /* Error - if this were accepted, it would be confusing which object i refers to */
+    return i;
+}