common/strtol: add strict_iecstrtoll; strict_sistrtoll uses base 10

common/strtol: add strict_iecstrtoll; strict_sistrtoll uses base 10

This adds parsing of iec units (IEC units Ki, Mi, ...) besides the parsing
of the usual unit multipliers (SI units K, M, ...). Both unit prefixes are
parsed with base 2. While SI units should be parsed with base 10, this
would likely confuse users.

Signed-off-by: Jan Fajerski <jfajerski@suse.com>