[ft-devel] FT_Bitmap_Convert: source == target >> boooom?

[armin]

I assume that `source != target' is true for `FT_Bitmap_Convert' (esp. since
there is some reallocating going on).  I suggest putting a quick note into
the docs to clarify that and probably extend the entry check:

```
diff --git a/src/base/ftbitmap.c b/src/base/ftbitmap.c
index c04eec43..6037538d 100644
--- a/src/base/ftbitmap.c
+++ b/src/base/ftbitmap.c
@@ -528,7 +528,7 @@
     if ( !library )
       return FT_THROW( Invalid_Library_Handle );

-    if ( !source || !target )
+    if ( !source || !target || source == target )
       return FT_THROW( Invalid_Argument );

     memory = library->memory;
'''

Further, I believe that similar rules apply to `FT_Bitmap_Blend'.