[ticket/11843] Add checking DEFINE variables with underscores to template_test

To prevent the underscore in DEFINE variables from being forgotten again,
the template tests now test INCLUDEing a file based on the contents of a
DEFINE variable with underscores in it.

PHPBB3-11843

tests/template/template_test.php

@@ -237,7 +237,7 @@ class phpbb_template_template_test extends phpbb_template_template_test_case
 				array('VARIABLE' => 'variable.html'),
 				array(),
 				array(),
-				'variable.html',
+				'variable.htmlvariable.html',
 			),
 			array(
 				'include_loop_define.html',

tests/template/templates/include_define_variable.html

@@ -1,2 +1,4 @@
 <!-- DEFINE $DEF = '{VARIABLE}' -->
 <!-- INCLUDE {$DEF} -->
+<!-- DEFINE $DEF_WITH_UNDERSCORES = '{VARIABLE}' -->
+<!-- INCLUDE {$DEF_WITH_UNDERSCORES} -->