On OpenBSD, use FILE_MAP_OPTIMIZED.

This has the effect of not performing a tt call each time in
ResolveLocalPathName() if we're on the local host anyway.  Drastically reduces
dtfile startup time.

cde/programs/dtfile/Imakefile

@@ -24,6 +24,10 @@ SYS_LIBRARIES = DtClientSysLibs DtClientExtraLibs
 EXTRA_DEFINES = -D_TOOLTALK
 #endif
 
+#ifdef OpenBSDArchitecture
+EXTRA_DEFINES = -DFILE_MAP_OPTIMIZE
+#endif
+
 #if defined (SunArchitecture)
 EXTRA_CCOPTIONS = -xF
 #endif