gdb/fortran: Use TYPE_CODE_CHAR for character types

gdb/fortran: Use TYPE_CODE_CHAR for character types

Switch to using TYPE_CODE_CHAR for character types.  This appears to
have little impact on the test results as gFortran uses the
DW_TAG_string_type to represent all character variables (as far as I
can see).  The only place this has an impact is when the user casts a
variable to a character type, in which case GDB does now use the CHAR
type, and prints the variable as both a value and a character, for
example, before:

    (gdb) p ((character) 97)
    $1 = 97

and after:

    (gdb) p ((character) 97)
    $1 = 97 'a'

gdb/ChangeLog:

	* f-lang.c (build_fortran_types): Use TYPE_CODE_CHAR for character
	types.

gdb/testsuite/ChangeLog:

	* gdb.fortran/type-kinds.exp: Update expected results.