jit,docs: various fixes

jit,docs: various fixes

gcc/jit/ChangeLog:

	* docs/cp/intro/tutorial02.rst: Use proper reference.
	* docs/cp/topics/contexts.rst: Likewise.
	* docs/cp/topics/functions.rst: Put `class` directive before a
	function as it is not allowed declaring a class in a fn.
	* docs/cp/topics/types.rst: Add template keyword.
	* docs/examples/tut04-toyvm/toyvm.c (toyvm_function_compile):
	Add removed comment used for code snippet ending detection.
	* docs/intro/tutorial04.rst: Fix to match the real comment.