libsyntax: fix parse fail tests.

Some tests now stop early, and produce only one error message

Author: matklad

src/test/parse-fail/associated-types-project-from-hrtb-explicit.rs

@@ -21,7 +21,6 @@ pub trait Foo<T> {
 
 fn foo2<I>(x: <I as for<'x> Foo<&'x isize>>::A)
     //~^ ERROR expected identifier, found keyword `for`
-    //~| ERROR expected one of `::` or `>`
 {
 }
 

src/test/parse-fail/keywords-followed-by-double-colon.rs

@@ -12,5 +12,4 @@
 
 fn main() {
     struct::foo();  //~ ERROR expected identifier
-    mut::baz(); //~ ERROR expected identifier
 }

src/test/parse-fail/removed-syntax-field-let.rs

@@ -13,5 +13,4 @@
 struct s {
     let foo: (),
     //~^  ERROR expected identifier, found keyword `let`
-    //~^^ ERROR expected `:`, found `foo`
 }

src/test/parse-fail/removed-syntax-mut-vec-expr.rs

@@ -13,5 +13,4 @@
 fn f() {
     let v = [mut 1, 2, 3, 4];
     //~^  ERROR expected identifier, found keyword `mut`
-    //~^^ ERROR expected one of `!`, `,`, `.`, `::`, `;`, `]`, `{`, or an operator, found `1`
 }

src/test/parse-fail/removed-syntax-mut-vec-ty.rs

@@ -12,4 +12,3 @@
 
 type v = [mut isize];
     //~^  ERROR expected identifier, found keyword `mut`
-    //~^^ ERROR expected one of `!`, `(`, `+`, `::`, `;`, `<`, or `]`, found `isize`

src/test/parse-fail/removed-syntax-uniq-mut-expr.rs

@@ -13,5 +13,4 @@
 fn f() {
     let a_box = box mut 42;
     //~^  ERROR expected identifier, found keyword `mut`
-    //~^^ ERROR expected one of `!`, `.`, `::`, `;`, `{`, or an operator, found `42`
 }

src/test/parse-fail/removed-syntax-uniq-mut-ty.rs

@@ -12,4 +12,3 @@
 
 type mut_box = Box<mut isize>;
     //~^  ERROR expected identifier, found keyword `mut`
-    //~^^ ERROR expected one of `!`, `(`, `+`, `,`, `::`, `<`, or `>`, found `isize`

src/test/parse-fail/unsized2.rs

@@ -17,6 +17,4 @@ fn f<X>() {}
 pub fn main() {
     f<type>();
     //~^ ERROR expected identifier, found keyword `type`
-    //~^^ ERROR: chained comparison
-    //~^^^ HELP: use `::<
 }

src/test/parse-fail/use-as-where-use-ends-with-mod-sep.rs

@@ -11,4 +11,3 @@
 // compile-flags: -Z parse-only
 
 use std::any:: as foo; //~ ERROR expected identifier, found keyword `as`
-//~^ ERROR: expected one of `::`, `;`, or `as`, found `foo`