sane.ds: Declare a function static

[Andrew Talbot]

Changelog:
    sane.ds: Declare a function static.

diff -urN a/dlls/sane.ds/sane_main.c b/dlls/sane.ds/sane_main.c
--- a/dlls/sane.ds/sane_main.c	2006-09-29 15:48:43.000000000 +0100
+++ b/dlls/sane.ds/sane_main.c	2007-01-26 22:38:34.000000000 +0000
@@ -66,7 +66,7 @@
 static TW_UINT16 SANE_OpenDS( pTW_IDENTITY, pTW_IDENTITY);
 #endif
 
-TW_UINT16 SANE_SourceControlHandler (
+static TW_UINT16 SANE_SourceControlHandler (
            pTW_IDENTITY pOrigin,
            TW_UINT16    DAT,
            TW_UINT16    MSG,