scp: fix build with gcc >= 14.x

Fixes build errors seen with gcc 14.x:

src/scp.c: In function ‘sink’:
src/scp.c:1214:32: error: implicit declaration of function ‘ascii_isdigit’
 [-Wimplicit-function-declaration]

src/scp.c: In function ‘okname’:
src/scp.c:1501:22: error: implicit declaration of function ‘ascii_isalpha’
 [-Wimplicit-function-declaration]

Patch provided by SVoxel: #473

Signed-off-by: Bernd Kuhls <bernd@kuhls.net>

Author: Voxel

src/scp.c

@@ -81,6 +81,7 @@
 #include "compat.h"
 #include "scpmisc.h"
 #include "progressmeter.h"
+#include "dbutil.h"
 
 void bwlimit(int);