Make VBO optimization partially optional

Yuck, there is a vertexbuffer being built on static init -.-

indra/newview/app_settings/settings_ascent.xml

@@ -3,6 +3,17 @@
 	<map>
 		<!-- Ascent-Specific Settings -->
 		
+		<key>SianaRenderOmitBlankVBO</key>
+		<map>
+			<key>Comment</key>
+			<string>Optimization: omit prefilling VBOs with zeroes. Default: OFF</string>
+			<key>Persist</key>
+			<integer>1</integer>
+			<key>Type</key>
+			<string>Boolean</string>
+			<key>Value</key>
+			<integer>0</integer>
+		</map>
 		<key>SianaUnsitOnCamReset</key>
 		<map>
 			<key>Comment</key>