Bug#55873 short startup options do not work in 5.5

Before this fix, the server did not recognize 'short' (as in -a)
options but only 'long' (as in --ansi) options
in the startup command line, due to earlier changes in 5.5
introduced for the performance schema.

The root cause is that handle_options() did not honor the
my_getopt_skip_unknown flag when parsing 'short' options.

The fix changes handle_options(), so that my_getopt_skip_unknown is
honored in all cases.

Note that there are limitations to this,
see the added doxygen documentation in handle_options().

The current usage of handle_options() by the server to
parse early performance schema options fits within the limitations.
This has been enforced by an assert for PARSE_EARLY options, for safety.

mysql-test/suite/perfschema/t/short_option_1.test

@@ -0,0 +1,35 @@
+# Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; version 2 of the License.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software Foundation,
+# 51 Franklin Street, Suite 500, Boston, MA 02110-1335 USA
+
+# Tests for PERFORMANCE_SCHEMA
+# Check server start for short server start options
+
+select 'Ok, the server started' as result;
+
+# See the associated -master.opt file.
+
+select @@SQL_MODE;
+show variables like 'sql_mode';
+
+select @@character_set_server;
+show variables like 'character_set_system';
+
+show variables like 'log';
+show variables like 'general_log';
+
+show variables like 'new';
+
+show variables like 'log_warnings';
+