Bump version to 1.5.0

[Earnie Boyd]

FYI, I bootstrapped msys tools by modifying the cygwin1.dll in the 
binary executable.  So, it's conceivable to postinstall a sed script 
that would modify the dll name with caveats of new functionality not 
supported.  I can also see the possibility for 32/64 bit versions for 
each new release with 32bit versions using libcygwin1.a while 64bit 
versions using libcygwin2.a.  An arbitrary date would be set to remove 
support for a 32bit versions.

Earnie.

Christopher Faylor wrote:
> 
> I know that we'd talked about changing to version 2 of cygwin, too, but
> that is going to be a pretty daunting task.  It means someone amongst us
> would have to write a cygwin1 wrapper DLL so as to not leave the old
> cygwin1 users behind.  It ideally means rebuilding the whole
> distribution with cygwin2 libraries.  It means stripping out all of the
> legacy code in cygwin1.dll (rewarding as that would be).
>