* Rename internal identifier from TTY_NR to just TTY
* Unify column header on platforms
* Use devname(3) on BSD derivate to show the actual terminal,
simplifies current FreeBSD implementation.
* Use 'unsigned long int' as id type, to fit dev_t on Linux.
Only on Solaris the terminal path is not yet resolved.
This prefers the `#if defined()` syntax over the `#ifdef` variant
whenever there's also a `#elif defined()` clause, thus making the
multiple branching structure more obvious and the overall use
more consistent.
If currently two unsigned values are compared via `a - b`, in the case b
is actually bigger than a, the result will not be an negative number (as
-1 is expected) but a huge positive number as the subtraction is an
unsigned subtraction.
Avoid over-/underflow affected operations; use comparisons.
Modern compilers will generate sane code, like:
xor eax, eax
cmp rdi, rsi
seta al
sbb eax, 0
ret
The MIN, MAX, CLAMP, MINIMUM, and MAXIMUM macros appear
throughout the codebase with many re-definitions. Make
a single copy of each in a common header file, and use
the BSD variants of MINIMUM/MAXIMUM due to conflicts in
the system <sys/param.h> headers.
