Remove unnecessary '\'.

Hi,
In proc mi_child_regexp, \(,thread-id=\"\[0-9\]+\") is appended to
children_exp, while the first '\' is not necessary.  This patch
is to remove it.  With this patch applied, Emacs can find the right
left paren.

gdb/testsuite:

2013-11-19  Yao Qi  <yao@codesourcery.com>

	* lib/mi-support.exp (mi_child_regexp): Remove unnecessary '\'.

gdb/testsuite/ChangeLog

@@ -1,3 +1,7 @@
+2013-11-19  Yao Qi  <yao@codesourcery.com>
+
+	* lib/mi-support.exp (mi_child_regexp): Remove unnecessary '\'.
+
 2013-11-19  Yao Qi  <yao@codesourcery.com>
 
 	* lib/mi-support.exp: Fix format.

gdb/testsuite/lib/mi-support.exp

@@ -1414,12 +1414,12 @@ proc mi_child_regexp {children add_child} {
 	    set value [lindex $item 4]
 
 	    lappend children_exp\
-		"$pre{name=\"$name\",exp=\"$exp\",numchild=\"$numchild\",value=\"$value\",type=\"$type\"\(,thread-id=\"\[0-9\]+\")?}"
+		"$pre{name=\"$name\",exp=\"$exp\",numchild=\"$numchild\",value=\"$value\",type=\"$type\"(,thread-id=\"\[0-9\]+\")?}"
 	} elseif {[llength $item] == 4} {
 	    set type [lindex $item 3]
 
 	    lappend children_exp\
-		"$pre{name=\"$name\",exp=\"$exp\",numchild=\"$numchild\",type=\"$type\"\(,thread-id=\"\[0-9\]+\")?}"
+		"$pre{name=\"$name\",exp=\"$exp\",numchild=\"$numchild\",type=\"$type\"(,thread-id=\"\[0-9\]+\")?}"
 	} else {
 	    lappend children_exp\
 		"$pre{name=\"$name\",exp=\"$exp\",numchild=\"$numchild\"(,thread-id=\"\[0-9\]+\")?}"