Faster detection of wrong table names (like PRN) on windows


include/my_sys.h:
  Added check_if_legal_filename()
mysys/my_access.c:
  Added check_if_legal_filename()
  Set errno if my_access() fails
mysys/my_fopen.c:
  USe check_if_legal_filename() instead of my_access() to detect wrong file names on windows
mysys/my_open.c:
  USe check_if_legal_filename() instead of my_access() to detect wrong file names on windows
sql/sql_lex.cc:
  Portability fix
sql/sql_parse.cc:
  Simple cleanup
sql/sql_repl.cc:
  Cleanup during code review