commented out the HHC_LOCATION line, as there are no easy to use alternatives for

hhc.exe on linux.
we should either run the chm build on a windows box(maybe on the replacement of oti1),
or look into running it through wine see
http://cweiske.de/tagebuch/Generating%20CHM%20files%20with%20Wine%20on%20a%20Linux%20server,%20and%20a%20bit%20about%20PEAR's%20PhD%20transition.htm
for details.
I also set DOT_CLEANUP to NO as the doc generation was spitting out errors regarding some dot
file cannot be found.

ext/spl/doxygen.cfg

@@ -111,7 +111,7 @@ HTML_STYLESHEET        =
 HTML_ALIGN_MEMBERS     = YES
 GENERATE_HTMLHELP      = YES
 CHM_FILE               = ../spl.chm
-HHC_LOCATION           = hhc.exe
+#HHC_LOCATION           = hhc.exe
 GENERATE_CHI           = NO
 BINARY_TOC             = NO
 TOC_EXPAND             = NO
@@ -210,7 +210,7 @@ MAX_DOT_GRAPH_WIDTH    = 1200
 MAX_DOT_GRAPH_HEIGHT   = 1024
 MAX_DOT_GRAPH_DEPTH    = 0
 GENERATE_LEGEND        = YES
-DOT_CLEANUP            = YES
+DOT_CLEANUP            = NO
 #---------------------------------------------------------------------------
 # Configuration::additions related to the search engine   
 #---------------------------------------------------------------------------