Implement missing miner functions on FreeBSD

[vasild]

Implement missing miner functions on FreeBSD

cryptonote::miner::get_system_times(): Fetch the system's total and
idle time using sysctl kern.cp_time.

cryptonote::miner::get_process_time(): Use the same implementation as
Linux and OSX, the times(3) function conforms to POSIX.1 and is
available on FreeBSD.

cryptonote::miner::on_battery_power(): Try to fetch the battery status
using sysctl hw.acpi.acline. If that fails (if ACPI is not enabled on
the system), then try querying /dev/apm.

[moneromooo-monero]

OK, though I'm not sure we want error messages if we fail to probe though, that might spam a bit on machines where it triggers ?

[vasild]

Errors from get_system_times() are not repeated and they are followed by another message clearly stating that mining is stopped: "get_system_times call failed, background mining will NOT work!".

Errors from on_battery_power() are indeed spamming the log every 10 seconds. I see that the Linux implementation of that function uses a mixture of LOG_PRINT_L0() and LOG_ERROR(). Should I leave it as is or convert the FreeBSD errors from LOG_ERROR() to LOG_PRINT_L0()?

[moneromooo-monero]

Level based messages (LOG_PRINT_Lx) are the original code, which was replaced with severity based messages (MERROR, MDEBUG, etc). The latter are prefered, and there is mapping from level based to severity based to avoid a huge pointless patch. LOG_ERROR probably points to MERROR, so is prefered over LOG_PRINT_L0 too in new code.

[vasild]

I see. So this patch is good to go or requires some adjustments?

[moneromooo-monero]

It's fine, thanks.

[fluffypony]

Reviewed