More robust check for '-F pandoc-filters', allowing pathnames.
Updated make_osx_package.sh.
Updated windows installer batch file.
Windows:  make citation support a separable component.
Further fixes to make_osx_package.sh.
changelog:  Added some citation-related entries.

These properly relate to pandoc-citeproc, but will be of
interest to pandoc users.
Typo in changelog.
Markdown reader:  unresolved citations fall back to original text.

Not ???.

Reason:  Less surprising, especially for people using @ as
in twitter.