Turn off REFERENCED_BY_RELATION and REFERENCES_RELATION

Those create a lot of output (basically what method uses what other method
and what method is used by what other method), which I doubt a whole lot
of people find useful.  Turning them off makes the html output much more
pleasant to read.

doc/doxygen/Doxystyle

@@ -107,8 +107,8 @@ INTERNAL_DOCS          = YES
 # then setting the SHOW_DIRECTORIES tag to YES will show the directory hierarchy
 # in the documentation. The default is NO.
 
-REFERENCED_BY_RELATION = YES
-REFERENCES_RELATION    = YES
+REFERENCED_BY_RELATION = NO
+REFERENCES_RELATION    = NO
 ALPHABETICAL_INDEX     = YES
 COLS_IN_ALPHA_INDEX    = 3
 HTML_OUTPUT            = html