Log Message:
utf8-cpp: updated to 3.2.1

Release 3.2.1
The release contains the fix the inclusion of both cpp11 and cpp17 headers on \ 
C++17 compilation. Also some additional tests for using string literals and \ 
string objects with modern compilers.

Release 3.2
Optional support for C++ 17 std::string_view.

Release 3.1.2
Fix for Issue 72.

Release 3.1.1
Include the commits from the previous year.

Release 3.1
This release adds one new API call: unchecked::replace_invalid().

Other changes are mostly about testing and installation.

Release 3.0.3
A minor release that contains fix for Issue 31 Program fails to link when \ 
including utf8.h in multiple files.

Release 3.0.2
This minor release contains:

Fix of the project version number at CMakeLists.txt
Continuous Integration with Google Tests and CircleCI

Release 3.0.1
A minor release with a fix for a header guard.

Release 3.0
This is a major release that introduces the following functionality:

New convenience API for C++ 11 and later compilers. The library still works with \ 
C++ 98/03 compliant compilers, just without the new functions.
advance() function works in both directions.
The following deprecated functions were removed:

previous() - deprecated since version 1.02.
is_bom() - deprecated since version 2.3.