Support multiple extra HTML stylesheets.

In regular use it happens that it is more convenient to have multiple extra HTML stylesheets, e.g. in case of different levels of requirements: company, department, project
With this patch it is possible to specify multiple HTML stylesheets.
Note: for compatibility the configuration parameter HTML_EXTRA_STYLESHEET has not been renamed to HTM_EXTRA_STYLESHEETS.

Merge branch 'feature-groupbreadcrumbs' of https://github.com/NimbusKit/doxygen into NimbusKit-feature-groupbreadcrumbs

Bug 728740 - XML Output: Doxygen doesn’t escape & characters (included in a hyperlink) in <detaileddescription>

Bug 734077 - no uniquely matching class member found for inline function definition where parameter argument names don't match

removeRedundantWhiteSpace micro-optimization

Error linking 32-bit windows

On Windows there were unresolved debug symbols resulting from libcpmtd. Adding this file to the ignore list solves the link issue. Remains:
LINK : warning LNK4098: defaultlib 'LIBCMT' conflicts with use of other libs; use /NODEFAULTLIB:library
even though libcmt is added.

Bug 733856 - segfault in QGListIterator while parsing fortran code