Minor patches for lib/missing and README

[Simon Sobisch]

I'm not sure where this file originates from but as I've just use this 
repository to update the file I post the "fix" here.
If it is the wrong place (the file doesn't include any hint where to post 
patches) please forward it.

-perl_URL=http://www.perl.org/
+perl_URL=https://www.perl.org/
-flex_URL=http://flex.sourceforge.net/
+flex_URL=https://github.com/westes/flex
 gnu_software_URL=https://www.gnu.org/software


Minor one for http://git.savannah.gnu.org/cgit/automake.git/tree/README

     Where to send patches, and discuss the automake development process
-    and the  design of new features.
+    and the design of new features.

Simon