Better Unicode support in GeneralUtils (#658)

* ASCIIToUTF16: output replacement character instead of failing assert

* Add GeneralUtils::_NextUTF8Char

* Implement GeneralUtils::UTF8ToUTF16

* use string_view everywhere

* use string_view::front instead of begin

* Add PushUTF16CodePoint

tests/CMakeLists.txt

@@ -4,6 +4,7 @@ create_test_sourcelist (Tests
 	AMFDeserializeTests.cpp
 	TestNiPoint3.cpp
 	TestLDFFormat.cpp
+	TestEncoding.cpp
 )
 
 # add the executable