[ft] Making the glyph_name argument of FT_Get_Name_Index const

[Antony Lee]

Hi all,
Would it be possible to make the glyph_name argument to FT_Get_Name_Index
const?  It is, after all, used essentially for a lookup and it would be
unexpected for the function to mutate it.  Obviously this does not restrict
any previously valid use; this simply additionally allows one to pass a
const FT_String* to FT_Get_Name_Index.
It looks like a simple search-replace of "FT_String\*  glyph_name" to
"const FT_String*  glyph_name" is sufficient; I am happy to provide a
proper patch if this change is agreed.
Antony