#3 Unbreak the build in C++17 mode

[Alexey Dokuchaev]

classes/gui/dialogs/colordlg.cpp uses the register keyword in several places which has been long deprecated and no longer accepted as of C++17 (Clang 16 now defaults to it). Consider removing it in the next version.

[Robert Kausch]

Thanks, this has been fixed in commit fe60685.