Add missing public interface for t_char_workaround (!106)

## What is the bug
The `t_char_workaround` was missing from the public interface, which causes some BuildBots to fail.
## How do you fix it
Add `t_char_workaround` public interface to `fortran_support`.

Approved by: Pradipta Samanta <samanta@dkrz.de>
Merged-by: Pradipta Samanta <samanta@dkrz.de>
Changelog: default

src/fortran_support.F90

@@ -67,6 +67,9 @@ MODULE fortran_support
   USE mo_util_table, ONLY: initialize_table, finalize_table, add_table_column, &
     & set_table_entry, print_table, t_table, t_column
   USE mo_util_texthash, ONLY: text_hash, text_hash_c, text_isEqual, sel_char
+#if defined(__PGI) || defined(__FLANG)
+  USE mo_util_texthash, ONLY: t_char_workaround
+#endif
   USE mo_util_timer, ONLY: util_cputime, util_walltime, util_gettimeofday, &
     & util_init_real_time, util_get_real_time_size, util_read_real_time, &
     & util_diff_real_time
@@ -164,6 +167,9 @@ MODULE fortran_support
 
   ! From mo_util_texthash
   PUBLIC :: text_hash, text_hash_c, text_isEqual, sel_char
+#if defined(__PGI) || defined(__FLANG)
+  PUBLIC :: t_char_workaround
+#endif
 
   ! From mo_util_timer
   PUBLIC :: util_cputime, util_walltime, util_gettimeofday, &