Minor documentation improvement. Based on a suggestion from Lawrence D'Oliveiro <ldo@geek-central.gen.nz>.
diff --git a/include/ftmodapi.h b/include/ftmodapi.h
index 95aef3a..2ef3f46 100644
--- a/include/ftmodapi.h
+++ b/include/ftmodapi.h
@@ -469,7 +469,9 @@ FT_BEGIN_HEADER
/* <Description> */
/* This function is used to create a new FreeType library instance */
/* from a given memory object. It is thus possible to use libraries */
- /* with distinct memory allocators within the same program. */
+ /* with distinct memory allocators within the same program. Note, */
+ /* however, that the used @FT_Memory structure is expected to remain */
+ /* valid for the life of the @FT_Library object. */
/* */
/* Normally, you would call this function (followed by a call to */
/* @FT_Add_Default_Modules or a series of calls to @FT_Add_Module) */