This fixes a compilation failure in mysql_com.h, which doesn't have
'uint' alias visibile. Maybe worth while changing to unsigned int, but
the rest of functions that work with defaults files return int.


include/my_sys.h:
  Change the return type back to int (modify_defaults_file).
include/mysql_com.h:
  Change the return type back to int (modify_defaults_file).
mysys/default_modify.c:
  Change the return type back to int (modify_defaults_file).