patch [#34103]

from Lawrence D'Oliveiro (ldo)

More use of bool type, necessitating adding inclusion of BLI_utildefines.h, or moving it up in the inclusion order if it was already included, in various places
- storage.c: make some variables only used in bli_builddir local to that
- storage.c: BLI_file_descriptor_size should allow 0 as a valid file descriptor
- path_util.c: make pointers to non-reentrant storage returned from folder routines const, necessitating making variables holding these returned pointers const elsewhere as well
- path_util.c: BLI_string_to_utf8 closes iconv context in case of conversion error
-  blf_lang.c: fill_locales routine now has its own "languages" local variable to construct paths (was stealing internal storage belonging to BLI_get_folder before)

source/gameengine/Ketsji/KX_PythonInit.cpp

@@ -1888,7 +1888,7 @@ PyObject *initGamePlayerPythonScripting(const STR_String& progname, TPythonSecur
 	 * somehow it remembers the sys.path - Campbell
 	 */
 	static bool first_time = true;
-	char *py_path_bundle   = BLI_get_folder(BLENDER_SYSTEM_PYTHON, NULL);
+	const char * const py_path_bundle   = BLI_get_folder(BLENDER_SYSTEM_PYTHON, NULL);
 
 #if 0 // TODO - py3
 	STR_String pname = progname;