Move the setting for secnumdepth to the document classes; make the numbering
for the manual class go one deeper than it previously did (\subsection
entries will now be numbered); no change for howto documents.

This makes it easier to refer precisely to smaller sections using \ref.
diff --git a/Doc/texinputs/howto.cls b/Doc/texinputs/howto.cls
index ad376c6..127edc4 100644
--- a/Doc/texinputs/howto.cls
+++ b/Doc/texinputs/howto.cls
@@ -12,6 +12,7 @@
 %
 \LoadClass[twoside]{article}
 
+\setcounter{secnumdepth}{1}
 
 % Optional packages:
 %