[Devel] sfdriver.c needs to include sferrors.h

[Graham Asher]

Hello, FreeTypers. I'm breaking my long silence to point out a small problem
I have discovered while compiling the released version of FreeType 2.1.5 for
the Symbian OS.

The file sfdriver.c will not compile on its own. The fix is easy - add
'#include "sferrors.h"' as line 27 of the file.

When compiling FreeType on Symbian OS, using the standard tool chain, one
cannot use files like sfnt.c that #include other source files. The files
have always compiled separately in the past; this is a regression caused, I
think, by the use of a new token-pasting system for defining error code
macros.

Graham Asher