buffer_new_file() checks for error
list_new_fd() prevents editing directories
parse_cmd() correctly adds N globbed filenames
Tidy up filter_cmd -> filter_argv
Only expand/glob if shellglob is set
Change wordexp() -> glob()

This handles tilde expansion, braces and is quicker/safer than
wordexp.
Simplify ITER_WINDOWS()
Set ESCDELAY to zero - tim doesn't use escape-chords