Document the history of fdisk based on the original post to comp.unix.bsd by Julian Elischer [1] and the Mach 2.5 Installation notes [2].
I was unable to pin point the exact version of Mach the fdisk utility appeared as I could not find documentation older than version 2.5 & no source code or repo history.
fdisk utility appears as a separate utility[3] in v2.5. Due to this, I have avoided stating the exact version fdisk first appeared in Mach.
Add authors section.

[1] https://groups.google.com/d/topic/comp.unix.bsd/Hhi45vAHxDg/discussion
[2] ftp://ftp.mcs.vuw.ac.nz/doc/misc/mach-i386-doc/i386_install.ps
[3] ftp://ftp.mcs.vuw.ac.nz/doc/misc/mach-i386-doc/i386_manpages.ps

PR: 212470
Approved by: bcr (mentor)
MFC after: 5 days
Differential Revision: https://reviews.freebsd.org/D8104