std: Remove i18n/l10n from format!

* The select/plural methods from format strings are removed
* The # character no longer needs to be escaped
* The \-based escapes have been removed
* '{{' is now an escape for '{'
* '}}' is now an escape for '}'

Closes #14810
[breaking-change]

src/libsyntax/ext/asm.rs

@@ -143,6 +143,7 @@ pub fn expand_asm(cx: &mut ExtCtxt, sp: Span, tts: &[ast::TokenTree])
                     inputs.push((constraint, input));
                 }
             }
+            #[cfg(stage0)]
             Clobbers => {
                 let mut clobs = Vec::new();
                 while p.token != token::EOF &&
@@ -164,6 +165,28 @@ pub fn expand_asm(cx: &mut ExtCtxt, sp: Span, tts: &[ast::TokenTree])
 
                 cons = clobs.connect(",");
             }
+            #[cfg(not(stage0))]
+            Clobbers => {
+                let mut clobs = Vec::new();
+                while p.token != token::EOF &&
+                      p.token != token::COLON &&
+                      p.token != token::MOD_SEP {
+
+                    if clobs.len() != 0 {
+                        p.eat(&token::COMMA);
+                    }
+
+                    let (s, _str_style) = p.parse_str();
+                    let clob = format!("~{{{}}}", s);
+                    clobs.push(clob);
+
+                    if OPTIONS.iter().any(|opt| s.equiv(opt)) {
+                        cx.span_warn(p.last_span, "expected a clobber, but found an option");
+                    }
+                }
+
+                cons = clobs.connect(",");
+            }
             Options => {
                 let (option, _str_style) = p.parse_str();