DtSvc/dtwm: Fix some implicit declarations of functions by adding appropriate

Patch from Frederic Koehler <f.koehler427@gmail.com>:

These implicit definitions cause segfaults on x64 because
the implicit return type is a 32-bit signed int, rather than a pointer
type.

cde/lib/DtSvc/DtUtil1/DtsMM.c

@@ -43,6 +43,7 @@
 #include <sys/param.h>
 #endif
 #include <string.h>
+#include <libgen.h>
 #define X_INCLUDE_DIRENT_H
 #define XOS_USE_XT_LOCKING
 #include <X11/Xos_r.h>

cde/lib/DtSvc/DtUtil1/DtsMM.h

@@ -137,6 +137,10 @@ extern	int	use_in_memory_db;
 extern	DtDtsMMDatabase		*_DtDtsMMGet(const char *name);
 extern	char			**_DtDtsMMListDb(void);
 
+/* FIXME: document */
+extern int *_DtDtsMMGetDbName(DtDtsMMDatabase *db, DtShmBoson boson);
+
+
 /* Name Comparison functions:
  * These routines can be passed in to the corresponding sort function to
  * sort by name.