Log Message:
exiv2: update to 0.27.3.

Headline Features of Exiv2 v0.27.3
----------------------------------

Thank you to Phil, Sridhar, Luis, Kevin, and Andreas S for working with me on \ 
the release.
As always, thanks to my wife Alison and our cat Lizzie for their support.

I am writing a book called Image Metadata and Exiv2 Architecture.
Current Draft: https://clanmills.com/exiv2/book/
               https://clanmills.com/exiv2/book/IMaEA.pdf

1) Bug and security fixes:
   - Security fixes
   - Improved Unicode/charset handling in comments
   - Improved lens recognition
   - Updated Catalan and Dutch localisation

2) Changes to downloadable build bundles:
   - Revised documentation and man page
   - Replace license.txt with COPYING
   - Removed contrib/ directory from bundle
   - share/locale has localisation files
   - msvc bundle built with vs2019

3) Build and Test:
   - Support for C++11 and C++14
   - Improved test harness and documentation
   - Test support for Visual Studio
   - Cross compiling support
   - UNIX support (Solaris, FreeBSD and NetBSD)
   - Http test support

4) Additions:
   - contrib/vs2019 Visual Studio support
   - contrib/Qt Qt sample project
   - .github/CONTRIBUTORS file
   - Defined security process (TBD)