Replace illegal with invalid in most diagnostics

src/test/compile-fail/bad-expr-lhs.rs

@@ -9,12 +9,12 @@
 // except according to those terms.
 
 fn main() {
-    1 = 2; //~ ERROR illegal left-hand side expression
-    1 += 2; //~ ERROR illegal left-hand side expression
-    (1, 2) = (3, 4); //~ ERROR illegal left-hand side expression
+    1 = 2; //~ ERROR invalid left-hand side expression
+    1 += 2; //~ ERROR invalid left-hand side expression
+    (1, 2) = (3, 4); //~ ERROR invalid left-hand side expression
 
     let (a, b) = (1, 2);
-    (a, b) = (3, 4); //~ ERROR illegal left-hand side expression
+    (a, b) = (3, 4); //~ ERROR invalid left-hand side expression
 
-    None = Some(3); //~ ERROR illegal left-hand side expression
+    None = Some(3); //~ ERROR invalid left-hand side expression
 }

src/test/compile-fail/issue-13407.rs

@@ -14,6 +14,6 @@ mod A {
 
 fn main() {
     A::C = 1;
-    //~^ ERROR: illegal left-hand side expression
+    //~^ ERROR: invalid left-hand side expression
     //~| ERROR: mismatched types
 }

src/test/compile-fail/old-suffixes-are-really-forbidden.rs

@@ -9,6 +9,6 @@
 // except according to those terms.
 
 fn main() {
-    let a = 1_is; //~ ERROR illegal suffix
-    let b = 2_us; //~ ERROR illegal suffix
+    let a = 1_is; //~ ERROR invalid suffix
+    let b = 2_us; //~ ERROR invalid suffix
 }

src/test/compile-fail/regions-name-static.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-struct Foo<'static> { //~ ERROR illegal lifetime parameter name: `'static`
+struct Foo<'static> { //~ ERROR invalid lifetime parameter name: `'static`
     x: &'static isize
 }