Fix build with texinfo 5+
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=718821
https://github.com/dankelley/gri/commit/93a40c0b444fb5265b21a344b884b1c7bed49b5a
--- doc/gri.texi.orig
+++ doc/gri.texi
@@ -18486,7 +18486,7 @@ Versions exist for MSDOS, windows, and Linux operating systems.
 (Actually, the windows version is just the MSDOS version, which can be
 run inside an msdos window within windows-95, windows-NT, etc.)
 
-@subsubsection MSDOS Operating System
+@subsection MSDOS Operating System
 @cindex compilation under MSDOS
 @cindex MSDOS compilation
 
@@ -18543,7 +18543,7 @@ To view the output, use a PostScript viewer such as GSview.
 
 
 
-@subsubsection LINUX Operating System
+@subsection LINUX Operating System
 @cindex compilation under Linux
 @cindex linux compilation
 @cindex LINUX compilation