qdoc: Remove CR from command parameters

Although it is not recommended, it is allowed to have a carriage
return in a qdoc command parameter that is enclosed in curly
braces. qdoc is supposed to use QString::simplified() to sanitize the
string so that all whitespace is replaced by a single ' '. But in at
least one case, this didn't work, and the carriage return was left in
the string, which caused qdoc to report that it couldn't find links
that have the carriage return in them. The problem has been fixed by
replacing the carriage return with a ' ' right when and where it is
detected.

Change-Id: I31c31f19a1e4150b2e27613ecbac260c46a7109b
Task-number: QTBUG-42449
Reviewed-by: Topi Reiniö <topi.reinio@digia.com>
qdoc: Include source file and line number of links

Each entry in the link-to-link tables and in the
broken-links table now includes the source file
path of the file where the link or broken link
appears and the line number in that file. The
line number often refers to where the comment
that contains the link begins, so sometimes
the link or broken link appears further down in
that comment.

Change-Id: I692bfc173c8711bf26c9c59ad9771930c27e24a8
Task-number: QTBUG-41850
Reviewed-by: Topi Reiniö <topi.reinio@digia.com>