editors/imhex: Update to 1.8.0

• Add dependency on ftp/curl, x11-toolkits/gtk30, and so on
• Remove dependency on lang/gcc10
• Fetch the snapshots of xdgpp, libfmt, nativefiledialog, and yara that are new submodules of ImHex (devel/libfmt and security/yara cannot be used because ImHex 1.8.0 is imcompatible with the release versions of them)