* checks.adb: Make warnings on exceptions into errors in GNATprove mode.
* errout.adb: Implement [ and ] insertion characters.
* errout.ads: Document new [ and ] insertion characters.
* sem_ch12.adb, restrict.adb, frontend.adb, exp_ch7.adb: Minor
addition of ??? comment.
* lib-xref.adb, exp_util.adb, gnat1drv.adb: Minor reformatting
* exp_ch4.adb, sem_ch3.adb, sem_ch4.adb, sem_ch6.adb, sem_elab.adb,
sem_eval.adb, sem_res.adb, sem_util.adb, sem_attr.adb, sem_aggr.adb:
Make warnings on exceptions into errors in GNATprove mode.
* sem_dim.adb: Minor reformatting throughout Quote [ and ]
in error messages.