tools: add missing #include "unicode/putil.h"

* we use u_setDataDirectory() in "unicode/putil.h"
* at present, this header is indirectly included,
  but this will change in ICU 59
* no impact on past ICUs.
* this is an exact analog to #11753

PR-URL: #12078
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>

tools/icu/iculslocs.cc

@@ -55,6 +55,7 @@ Japanese, it doesn't *claim* to have Japanese.
 #include <unicode/ustdio.h>
 #include <unicode/ures.h>
 #include <unicode/udata.h>
+#include <unicode/putil.h>
 
 const char* PROG = "iculslocs";
 const char* NAME = U_ICUDATA_NAME;  // assume ICU data