Update to 5.5.1

Changelog:
Changes from %.5 to 5.5.1
-------------------------

Apart from a fix for a configuration problem finding singal names from
(some) recent versions of glibc, there are only minor changes.

Changes from 5.4.2 to 5.5
-------------------------

The effect of the NO_INTERACTIVE_COMMENTS option extends into $(...) and
`...` command substitutions when used on the command line.  Previously,
comments were always recognized within command substitutions unless the
comment character "#" was disabled via reset of $histchars.

An alternative assignment syntax for indicating indices for arrays
and keys for associative arrays:

typeset -a array=([1]=first [2]=second)
typeset -A assoc=([key1]=val1 [key2]=val2)

is allowed for compatibility with other shells.  In the case of normal
arrays the new syntax can be mixed with the old.

(ryoon)