Remove un-used add_character_to_string subroutine

 - Dead code--unreachable
 - Never called anywhere else
 - Not documented

Author: zbeekman

src/json_module.F90

@@ -7599,32 +7599,6 @@ subroutine parse_string(unit, str, string)
     end subroutine parse_string
 !*****************************************************************************************
 
-!*****************************************************************************************
-!.... gfortran bug ..... some problem.....
-!*****************************************************************************************
-    pure subroutine add_character_to_string(str,ip,c)
-
-    implicit none
-
-    character(kind=CK,len=:),allocatable,intent(inout) :: str
-    integer(IK),intent(inout) :: ip
-    character(kind=CK,len=1),intent(in) :: c
-
-    if (allocated(str)) then
-        !resize string if necessary:
-        if (ip>len(str)) str = str // repeat(space, chunk_size)
-    else
-        str = repeat(space, chunk_size)
-        ip = 1
-    end if
-
-    !append to string:
-    str(ip:ip) = c
-    ip = ip + 1
-
-    end subroutine add_character_to_string
-!*****************************************************************************************
-
 !*****************************************************************************************
 !****if* json_module/parse_for_chars
 !