Test issuing a command split in multiple lines with continuation chars

I happened to break this locally and the testsuite didn't notice it.
Add some tests.

gdb/ChangeLog:
2016-03-09  Pedro Alves  <palves@redhat.com>

	* gdb.base/command-line-input.exp: New file.

gdb/ChangeLog

@@ -1,3 +1,7 @@
+2016-03-09  Pedro Alves  <palves@redhat.com>
+
+	* gdb.base/command-line-input.exp: New file.
+
 2016-03-09  Marcin Kościelnicki  <koriakin@0x04.net>
 
 	* corefile.c (safe_read_memory_unsigned_integer): New function.

gdb/testsuite/gdb.base/command-line-input.exp

@@ -0,0 +1,36 @@
+# Copyright (C) 2016 Free Software Foundation, Inc.
+#
+# 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; either version 3 of the License, or
+# (at your option) any later version.
+#
+# 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, see <http://www.gnu.org/licenses/>.
+
+# Command line input testing.
+
+# Test issuing a command split in multiple lines with continuation
+# characters.
+
+gdb_exit
+gdb_start
+
+set test "print 1\\\\n + 2"
+gdb_test_multiple "print 1\\\n + 2" $test {
+    -re "^print 1\\\\\r\n \\+ 2\r\n\\\$$decimal = 3\r\n$gdb_prompt $" {
+	pass $test
+    }
+}
+
+set test "print 1\\\\n2"
+gdb_test_multiple "print 1\\\n2" $test {
+    -re "^print 1\\\\\r\n2\r\n\\\$$decimal = 12\r\n$gdb_prompt $" {
+	pass $test
+    }
+}