fix #555 detect mysqli

Detects if mysqli is present

layouts/v7/modules/Install/Step4.tpl

@@ -37,7 +37,11 @@
 								<td>{vtranslate('LBL_DATABASE_TYPE', 'Install')}<span class="no">*</span></td>
 								<td>
 									{vtranslate('MySQL', 'Install')}
-									<input type="hidden" value="mysql" name="db_type">
+									{if function_exists('mysqli_connect')}
+										<input type="hidden" value="mysqli" name="db_type">
+									{else}
+										<input type="hidden" value="mysql" name="db_type">
+									{/if}
 								</td>
 							</tr>
 							<tr>