Document command-line options file support in changes file

CHANGES.current

@@ -7,6 +7,15 @@ the issue number to the end of the URL: https://github.com/swig/swig/issues/
 Version 4.0.0 (in progress)
 ===========================
 
+2018-02-18: JPEWdev
+            Patch #1164 - Add support for a command-line options file, also sometimes
+            called a response file. This is useful if the command-line options exceed
+            the system command-line length limit. To use, put the command-line options
+            into a file, then provide the file name prefixed with @, for example using
+            a file called args.txt:
+
+              swig @args.txt
+
 2018-02-11: wsfulton
             [Javascript] #1187 Fix compilation error wrapping std::complex via
             std_complex.i.