include/freetype/freetype.h (FT_Encoding): Improve documentation.

Based on a suggestion by Antony Lee <anntzer.lee@gmail.com>.

include/freetype/freetype.h

@@ -730,11 +730,16 @@ FT_BEGIN_HEADER
    *     Same as FT_ENCODING_JOHAB.  Deprecated.
    *
    * @note:
-   *   By default, FreeType enables a Unicode charmap and tags it with
-   *   `FT_ENCODING_UNICODE` when it is either provided or can be generated
-   *   from PostScript glyph name dictionaries in the font file.  All other
-   *   encodings are considered legacy and tagged only if explicitly defined
-   *   in the font file.  Otherwise, `FT_ENCODING_NONE` is used.
+   *   When loading a font, FreeType makes a Unicode charmap active if
+   *   possible (either if the font provides such a charmap, or if FreeType
+   *   can synthesize one from PostScript glyph name dictionaries; in either
+   *   case, the charmap is tagged with `FT_ENCODING_UNICODE`).  If such a
+   *   charmap is synthesized, it is placed at the first position of the
+   *   charmap array.
+   *
+   *   All other encodings are considered legacy and tagged only if
+   *   explicitly defined in the font file.  Otherwise, `FT_ENCODING_NONE` is
+   *   used.
    *
    *   `FT_ENCODING_NONE` is set by the BDF and PCF drivers if the charmap is
    *   neither Unicode nor ISO-8859-1 (otherwise it is set to