Support more suggestions in template for bad attribute use

[estebank]

Modify

rust/src/libsyntax/feature_gate.rs

Lines 873 to 877 in a6ce9b3

	pub struct AttributeTemplate {
	word: bool,
	list: Option<&'static str>,
	name_value_str: Option<&'static str>,
	}

to allow for multiple suggestions of the same type.

The following

rust/src/test/ui/no_crate_type.stderr

Lines 1 to 5 in a6ce9b3

	error: malformed `crate_type` attribute input
	--> $DIR/no_crate_type.rs:2:1
	|
	LL | #![crate_type]
	| ^^^^^^^^^^^^^^ help: must be of the form: `#[crate_type = "bin|lib|..."]`

should be

error: malformed `crate_type` attribute input
  --> $DIR/no_crate_type.rs:2:1
   |
LL | #![crate_type]
   | ^^^^^^^^^^^^^^ malformed input
help: must be of the form:
   |
LL | #![crate_type = "bin"]
   |
LL | #![crate_type = "lib"]
   |
LL | #![crate_type = "..."]
   |