Fixed error starting with uppercase

Error messages cleaned in librustc/middle

Error messages cleaned in libsyntax

Error messages cleaned in libsyntax more agressively

Error messages cleaned in librustc more aggressively

Fixed affected tests

Fixed other failing tests

Last failing tests fixed

src/test/compile-fail/struct-no-fields.rs

@@ -9,6 +9,6 @@
 // except according to those terms.
 
 struct Foo {}
-//~^ ERROR: Unit-like struct definition should be written as `struct Foo;`
+//~^ ERROR: unit-like struct definition should be written as `struct Foo;`
 
 fn main() {}