[wwwdocs] adjust www.itl.nist.gov to https in readings.html

[Gerald Pfeifer]

Applied.

Gerald

Index: readings.html
===================================================================
RCS file: /cvs/gcc/wwwdocs/htdocs/readings.html,v
retrieving revision 1.294
diff -u -r1.294 readings.html
--- readings.html	2 Jun 2018 21:16:10 -0000	1.294
+++ readings.html	14 Jul 2018 21:31:53 -0000
@@ -414,9 +414,9 @@
       Some packages aimed at Fortran compiler validation.
     <ul>
       <li>
-        <a href="http://www.itl.nist.gov/div897/ctg/fortran_form.htm">FORTRAN
+        <a href="https://www.itl.nist.gov/div897/ctg/fortran_form.htm">FORTRAN
         77 test suite</a> by the NIST Information Technology Laboratory
-        (<a href="http://www.itl.nist.gov/div897/ctg/software.htm">license</a>)
+        (<a href="https://www.itl.nist.gov/div897/ctg/software.htm">license</a>)
         contains legal and operational Fortran 77 code.
       </li>
       <li>