Renaming the reconf script to align more closely with autotools 
standards.

There are certain conventions users expect when working with a project 
that uses autotools. Deviating from those conventions adds confusion and 
complexity to a project. krb5 deviates from those conventions in several 
ways. In an effort to try to simplify the krb5 build, I am moving and 
renaming the src/util/reconf script to src/bootstrap. The bootstrap name 
was chosen since the Autotools documentation says it is the preferred 
name. For more information on this please see:
    
https://goo.gl/JRvpYK
https://goo.gl/V1i521