Port #[patchable_function_entry] to attr parser

tests/ui/patchable-function-entry/patchable-function-entry-attribute.rs

@@ -1,17 +1,26 @@
 #![feature(patchable_function_entry)]
 fn main() {}
 
-#[patchable_function_entry(prefix_nops = 256, entry_nops = 0)]//~error: integer value out of range
+#[patchable_function_entry(prefix_nops = 256, entry_nops = 0)]
+//~^ ERROR malformed
 pub fn too_high_pnops() {}
 
-#[patchable_function_entry(prefix_nops = "stringvalue", entry_nops = 0)]//~error: invalid literal value
+#[patchable_function_entry(prefix_nops = "stringvalue", entry_nops = 0)]
+//~^ ERROR malformed
 pub fn non_int_nop() {}
 
-#[patchable_function_entry]//~error: malformed `patchable_function_entry` attribute input
+#[patchable_function_entry]
+//~^ ERROR malformed `patchable_function_entry` attribute input
 pub fn malformed_attribute() {}
 
-#[patchable_function_entry(prefix_nops = 10, something = 0)]//~error: unexpected parameter name
+#[patchable_function_entry(prefix_nops = 10, something = 0)]
+//~^ ERROR malformed
 pub fn unexpected_parameter_name() {}
 
-#[patchable_function_entry()]//~error: must specify at least one parameter
+#[patchable_function_entry()]
+//~^ ERROR malformed
 pub fn no_parameters_given() {}
+
+#[patchable_function_entry(prefix_nops = 255, prefix_nops = 255)]
+//~^ ERROR malformed
+pub fn duplicate_parameter() {}