Deprecate CI_Input::is_cli_request() and add common function is_cli() to replace it

Calls to this function are often needed before the Input library is available
diff --git a/tests/mocks/core/common.php b/tests/mocks/core/common.php
index e5dc29c..b073f23 100644
--- a/tests/mocks/core/common.php
+++ b/tests/mocks/core/common.php
@@ -190,4 +190,13 @@
 	{
 		return TRUE;
 	}
+}
+
+if ( ! function_exists('is_cli'))
+{
+	// In order to test HTTP functionality, we need to lie about this
+	function is_cli()
+	{
+		return FALSE;
+	}
 }
\ No newline at end of file
diff --git a/tests/mocks/core/uri.php b/tests/mocks/core/uri.php
index 94f75df..1107858 100644
--- a/tests/mocks/core/uri.php
+++ b/tests/mocks/core/uri.php
@@ -18,9 +18,4 @@
 
 	}
 
-	protected function _is_cli_request()
-	{
-		return FALSE;
-	}
-
 }
\ No newline at end of file