New port: math/bcal: Storage expression, unit conversion & address offset CLI calculator

bcal (Byte CALculator) is a REPL CLI utility for storage expressions, unit
conversions or address calculations. If you can't calculate the hex address
offset for (512 - 16) MiB, or the value when the 43rd bit of a 64-bit
address is set mentally, bcal is for you.

It has a bc mode for general-purpose numerical calculations.

bcal follows Ubuntu's standard unit conversion and notation policy. Only
64-bit operating systems are supported.

Features:

• evaluate arithmetic expressions involving storage units
• perform general purpose calculations (using bc)
• convert to IEC/SI standard data storage units
• interactive mode with the last valid result stored for reuse
• show the address in bytes
• show address as LBA:OFFSET
• convert CHS to LBA and vice versa
• base conversion to binary, decimal and hex
• custom sector size, max heads/cylinder and max sectors/track
• minimal dependencies

WWW: https://github.com/jarun/bcal

Reviewed by: mat
Approved by: mat (mentor)
Differential Revision: https://reviews.freebsd.org/D18556