Increase Portability to BSD

[btdn]

As described in the info page for GNU sort:

‘-g’
‘--general-numeric-sort’
‘--sort=general-numeric’
Sort numerically, converting a prefix of each line to a long
double-precision floating point number. *Note Floating point::.
Do not report overflow, underflow, or conversion errors. Use the
following collating sequence:

• Lines that do not start with numbers (all considered to be equal).
• NaNs (“Not a Number” values, in IEEE floating point arithmetic) in a consistent but machine-dependent order.
• Minus infinity.
• Finite numbers in ascending numeric order (with -0 and + equal).
• Plus infinity.

Use this option only if there is no alternative; it is much slower
than ‘--numeric-sort’ (‘-n’) and it can lose information when
converting to floating point.

It, however, is not portable.

md5sum and the flags for stat also aren't portable. I added commented out versions that work on NetBSD but, since an error at that point doesn't prevent the process from completing, I didn't bother with a more robust solution.