icu 50 and how to identify dependents

[Ryan Schmidt]

I'd like to upgrade the icu port to version 50. This changes the library version number so I'll need to revbump everything linking with it. Any tips on how to identify what ports those are? I know I can find ports declaring a dependency on icu with:

port file all | sort -u | xargs grep :icu

But what about ports not declaring a dependency? I also need to examine the dependents of every port that depends on icu don't I? For example pango was recently updated to 1.32.5, which for the first time uses harfbuzz, which uses icu, so now everything that uses pango also uses icu and needs a revbump. I think I want to explicitly add a port:icu dependency to all ports using pango to make these easier to find in the future.

I figure while we're already dealing with a chaos of revbumps and rebuilds due to jpeg 9 we may as well get icu 50 over with at the same time. Any objections?