Bug 700510 - Bibliography duplicate filenames fails

Problem in the bug report is that the bib files in the different directories have the same name and thus overwrite each other.
This patch solves this problem as well as the possibility to have spaces in the file name.
For all output formats the bib files are copied to a new numbered name: "bibTmpFile_<number>", for Latex on the LATEX_OUTPUT directory and for all other formats in the subdirectory "bibTmpDir" of the OUTPUT_DIRECTORY.
The files for Latex are retained whilst the files for the other formats are removed after usage (as it was before).
Bug 700510 - Bibliography duplicate filenames fails

Spaces are now allowed in the file names
Bug 734727 - GENERATE_TAGFILE no longer includes any @*section links

Changed the previous fix to allow references to sections defined in
a mainpage that is imported via a tag file.
Merge branch 'master' of github.com:doxygen/doxygen
Merge branch 'feature/bug_700510' of https://github.com/albert-github/doxygen into albert-github-feature/bug_700510
Fixed typo and used QString for directory
Merge branch 'albert-github-feature/bug_700510'
No warning in case cite definition is missing

In case the \cite command is used but no entry for it is given in a bib file no warning is given as the CiteInfo entry is present with the right label, but the text item is empty and this is not tested.

(also corrected an error message on opening a file)
Minor fixes
Merge branch 'albert-github-feature/bug_no_warning_on_cite'