[flang] Corrected expected value for empty STRING. (#359)

* Adding an executable test for the Fortran 2023 tokenize intrinsic.

* Corrected expected value for empty STRING.

---------

Co-authored-by: Kevin Wyatt <kwyatt@hpe.com>

Author: kwyatt-ext

Fortran/cray/f2023/16/09/tokenize01.reference_output

@@ -165,7 +165,7 @@
 
    ---- Test 7 - 4: TOKENIZE with FIRST and LAST ----
      FIRST   LAST
-         0      0
+         1      0
    ---- Test 7 - 5: TOKENIZE with TOKENS, but no SEPARATOR ----
    TOKENS:   
       ""
@@ -180,7 +180,7 @@
 
    ---- Test 8 - 4: TOKENIZE with FIRST and LAST ----
      FIRST   LAST
-         0      0
+         1      0
    ---- Test 8 - 5: TOKENIZE with TOKENS, but no SEPARATOR ----
    TOKENS:   
       ""