The earlier fix for the broken ios10 emoji font ended up breaking
messages for some users with a tall font.
Here we have a lighter touch - ensuring we don't touch messages that
don't use emoji.
Also, introduce a different approach to the fix, rather than trying to
compute the bounding rect of an appropriately attributed string, just
add an extra bit of height per line.
This approach isn't ideal for long messages with only one emoji line in
them, but the previous approach was incompatible with Chinese messages
that also contain emoji. See the new
`MesssagesBubblesSizeCalculatorTest.swift` for test cases considered.
// FREEBIE
bd370f1de4
