Don't need floor() in timeman.cpp

For positive numbers result is equivalent:
http://stackoverflow.com/questions/3300290/cast-to-int-vs-floor

Spotted by Joseph Ellis.

No functional change.
Remove other useless floor()

No functional change.
Minor stuff scattered around

Just random minor stuff I found while browsing the code.

No functional change.
Rearrange interpolation formula

Put the division at the end to reduce
rounding errors. This alters the bench
due to different rounding errors, but
should not alter ELO in any way.

bench: 7615217