[mkfs-msdosfs] add -T (timestamp) option for reproducible builds

This ports over this patch from FreeBSD in order to provide
custom timestamps when building a fat filesystem. This is one
small step towards getting our build system to make reproducible
builds.

https://github.com/freebsd/freebsd/commit/8255b708586c622eab1f692869b8067567f5cee9

TEST: Manually confirmed mkfs-msdosfs will create identical
files when run with the "-T ..." option.

Change-Id: I881ebd543b8086ec206f4d00f8de9031ff4a1760

mkfs-msdosfs: size option for writing into files

When creating full GPT images and/or writing to individual partitions on
a disk, it is useful to be able to write to a specific range of the
disk, given by offset (-@) and size (-S).

Change-Id: Ic0aadfe4e3bb130216d26e22a26f81ad1921bdc0

host: mkfs-msdosfs builds

Change-Id: Iee0f07eba9a0d94123b3db72460aa48d145059fa

[third-party][mkfs-msdosfs] Clang fmt mkfs

Since this is a fairly stable codebase which we have already modified
significantly (and most likely won't be resyncing with FreeBSD), update
the style to match the rest of the Magenta codebase.

Change-Id: I85fb57fd6a13f251032a2f3d84162b6497a20448

[third-party][mkfs-msdosfs] Modifications to build on Magenta

These modifications include:
- Removing informational signal handlers
- Removing ioctls
- Removing some command line options
- Altering types, attributes, and macros to Magenta equivalents

Change-Id: Iee2260e04fe625f7f06f34d9534ca1833ef59dfb

[third-party][mkfs-msdosfs] Exact copy of FreeBSD's 'newfs_msdos'

Change-Id: Id4385daf91a0fb641b848f9825aa4cd37f84b33d