new file added, giving some description of the documentation generation

* doc/README.docs, doc/Makefile.am: new file added,
  giving some description of the documentation generation process
* doc/search.php: fixed problem with upper case on filenames
diff --git a/doc/Makefile.am b/doc/Makefile.am
index b51354c..3b5ec2f 100644
--- a/doc/Makefile.am
+++ b/doc/Makefile.am
@@ -25,7 +25,8 @@
            tutorial/images/*.png tutorial/images/callouts/*.png \
 	   API*.html *.1 *.xsl *.html *.gif w3c.png html/*.html \
 	   html/*.png libxml2-api.xml parsedecl.py index.py search.php \
-	   apibuild.py libxml2.xsa xmllint.xml xmlcatalog_man.xml
+	   apibuild.py libxml2.xsa xmllint.xml xmlcatalog_man.xml \
+	   README.docs
 
 
 man_MANS = xmllint.1 xmlcatalog.1