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
auto merge of #12065 : mrshu/rust/error-formating-fix, r=alexcrichton

This pull request tries to fix #12050.

I went after these wrong errors quite aggressively so it might be that I also changed some strings that are not actual errors.

Please point those out and I will update this pull request accordingly.