clang-tidy: disable ppcoreguidelines-narrowing-conversions check
clang-tidy: disable ppcoreguidelines-narrowing-conversions check

Much like -Wconversions, should be enabled, but uncovers a lot of dirt
right now, so a lot of cleanup would be needed.

LebedevRI/rawspeed,darktable-org/rawspeed,darktable-org/rawspeed,darktable-org/rawspeed,LebedevRI/rawspeed,darktable-org/rawspeed,LebedevRI/rawspeed,LebedevRI/rawspeed,LebedevRI/rawspeed,darktable-org/rawspeed