[bootstrap-O3] add a default initializer to avoid a warning at -O3

Building with the bootstrap-O3 configuration option fails to compile
input.c due to an AFAICT false-positive warning about an uninitialized
use of a variable.

This patch adds a default initializer to silence it.

for  gcc/ChangeLog

	* input.c (assert_char_at_range): Default-initialize
	actual_range.

From-SVN: r244091

gcc/ChangeLog

 2017-01-04  Alexandre Oliva <aoliva@redhat.com>
 
+	* input.c (assert_char_at_range): Default-initialize
+	actual_range.
+
+2017-01-04  Alexandre Oliva <aoliva@redhat.com>
+
 	* df-scan.c (df_ref_create_structure): Make regno unsigned,
 	to match the caller.
 

gcc/input.c

@@ -2173,7 +2173,7 @@ assert_char_at_range (const location &loc,
   cpp_reader *pfile = test.m_parser;
   string_concat_db *concats = &test.m_concats;
 
-  source_range actual_range;
+  source_range actual_range = source_range();
   const char *err
     = get_source_range_for_char (pfile, concats, strloc, type, idx,
 				 &actual_range);