Release 2.7.1

Release 2.7.0

Release 2.7b1

Release 2.6.0

Release 2.6b1

Release 2.5.0

Release 2.5b1

improve converting strings to ints/longs

The existing code is inconsistent, and in a couple of cases wrong, about
dealing with strings that are not valid ints. For example, there are
locations that call wcstol() and check errno without first setting errno
to zero. Normalize the code to a consistent pattern.  This is mostly to
deal with inconsistencies between BSD, GNU, and other UNIXes.

This does make some syntax more liberal. For example `echo $PATH[1 .. 3]`
is now valid due to uniformly allowing leading and trailing whitespace
around numbers. Whereas prior to this change you would get a "Invalid
index value" error. Contrast this with `echo $PATH[ 1.. 3 ]` which was
valid and still is.

Release 2.4.0

Release 2.4b1