Added show_brackets to settings menu.

--- a/src/Pure/proof_general.ML	Tue Mar 25 09:58:51 2003 +0100
+++ b/src/Pure/proof_general.ML	Tue Mar 25 10:03:11 2003 +0100
@@ -285,6 +285,8 @@
       bool_option show_consts)),
    ("long-names", ("Whether to show fully qualified names in Isabelle.",
       bool_option long_names)),
+   ("show-brackets", ("Whether to show full bracketing in Isabelle.",
+      bool_option show_brackets)),
    ("eta-contract", ("Whether to print terms eta-contracted in Isabelle.",
       bool_option Syntax.eta_contract)),
    ("trace-simplifier", ("Whether to trace the Simplifier in Isabelle.",