Add change comments in SimpleDateFormat.

Add Android-changed/-removed/-added comments where appropriate in
java.text.SimpleDateFormat.

Note that SimpleDateFormat is currently in a hybrid state where some
upstream changes from 8u121-b30 are applied (mostly JavaDoc changes and
other changes that don't effect behaviour) but the rest of the file is
still at the level of 7u40 (notably, the additional OpenJDK 8 features
have not been merged).

Bug: 65669355
Bug: 66411240
Test: m (comment-only changes)
Change-Id: I2d0ba1901a12dad3d3dfd4c80c0421ad1027399a
1 file changed