[ticket/10970] Paths of the form {FOO}/a/{BAR}/b parsed correctly

A new method to handle this type of path was added and
compile_tag_include, compile_tag_include_php and
compile_tag_include_js were modified to use it appropriately.

Tests were added for these three macros also.

PHPBB3-10970

tests/template/templates/subdir/variable.html

@@ -0,0 +1 @@
+{VARIABLE}