Convert FORTRAN modules to namespaces

This helps fix linking issues and ambiguity related to the difference between classes and modules in FORTRAN 2003+.
Bug 740446 - invalid copydoc target does not result in warning
Support visible=no for main page tab.
LaTeX problem with 2 consecutive single quotes

In LaTeX 2 consecutive single quotes are joined to 1 double quote. This leads in texts where 2 single quotes are intended to a strange view. An example is the initial value for variables. E.g. in Fortran: character(len=10) :: A = ''  (i.e an empty string which can either be defined as '' or as "") or in C: char *sq  = "''". In the source listings this is OK but in the description text it was not OK.
Fix rules for closing FORTRAN module and typedef scopes
Bug ?? for page numbers in the latex indices

Due to the fact that the path was not stripped from the file name in case CREATE_SUBDIRS was set to YES there was a reference to a non existing page reference. In the corresponding hypertarget and label the path was already stripped.
Remove bogus argument to avoid compiler warning
Bug 687576 - Add support for LATEX_EXTRA_STYLESHEET

Added the possibility for  LATEX_EXTRA_STYLESHEET analogous to  HTML_EXTRA_STYLESHEET. Special attention has been paid to the extension as ".sty" is automatically added by the \usepackage
Removed some comment statements.
Merge pull request #249 from albert-github/feature/bug_latex_single_quotes

LaTeX problem with 2 consecutive single quotes
Merge pull request #252 from albert-github/feature/bug_latex_index_komal

Bug ?? for page numbers in the latex indices
Merge branch 'master' of github.com:doxygen/doxygen
Use result of vsnprintf
Merge pull request #248 from drobilla/master

Support visible=no for main page tab.
Merge branch 'master' of github.com:doxygen/doxygen
Remove filtering rule when generating FORTRAN module links
Fix bug: language switch command "\~" failed to detect language id which contains '-'

Support language switch for language ids, 'Japanese-en', 'Korean-en', 'Serbian-Cyrillic', and similer langauge ids.
Fixed typos in comments.
Merge pull request #255 from orbitcowboy/master

Fixed typos in comments.
Merge pull request #254 from kbinani/language_switch_command

Fix bug: language switch command skipped when langauge id contains "-" letter