Add missing const. (g_strsplit): Add g_return_val_if_fail for case of

* glib/gstrfuncs.c: (g_ascii_strdown), (g_ascii_strup): Add
	missing const.
	(g_strsplit): Add g_return_val_if_fail for case of empty
	delimiter, which can result in an infinite loop otherwise.
	* glib/gstrfuncs.h: Add missing const.
	* tests/.cvsignore: Ignore a generated file.

	* tests/array-test.c:
	* tests/dirname-test.c:
	* tests/hash-test.c:
	* tests/list-test.c:
	* tests/node-test.c:
	* tests/relation-test.c:
	* tests/shell-test.c:
	* tests/slist-test.c:
	* tests/spawn-test.c:
	* tests/strfunc-test.c:
	* tests/string-test.c:
	* tests/testglib.c:
	* tests/tree-test.c:
	* tests/type-test.c:
	Add an #undef G_DISABLE_ASSERT so all tests will assert even if
	asserts are disabled inside glib itself.

docs/reference/glib/tmpl/string_utils.sgml

@@ -359,17 +359,19 @@ nesting such as g_strup (g_strcanon (str)).
 <!-- ##### FUNCTION g_strsplit ##### -->
 <para>
 Splits a string into a maximum of @max_tokens pieces, using the given
-@delimiter. If @max_tokens is reached, the final string in the returned
-string array contains the remainder of @string.
+@delimiter. If @max_tokens is reached, the last piece contains the
+remainder of @string. If @string is an empty string, then the resulting
+string array has no elements.
 </para>
 
 @string: a string to split.
 @delimiter: a string which specifies the places at which to split the string.
 The delimiter is not included in any of the resulting strings, unless
 max_tokens is reached.
-@max_tokens: the maximum number of strings to split @string into. If this is
+@max_tokens: the maximum number of pieces to split @string into. If this is
 less than 1, the string is split completely.
-@Returns: a newly-allocated array of strings. Use g_strfreev() to free it.
+@Returns: a newly-allocated NULL-terminated array of strings. Use g_strfreev()
+to free it.
 
 
 <!-- ##### FUNCTION g_strfreev ##### -->