Optimize logging: reduce time lookups, stop using strftime()
Optimize logging: reduce time lookups, stop using strftime()

The time() call in _prepareLogEntry() was redundant because we already
call gettimeofday(). Profiling has also shown that strftime() is slow,
so now we use snprintf().

Logging is now 26% faster compared to the previous commit.
Together with the previous 3 commits, logging is now 95% faster.

clemensg/passenger,phusion/passenger,clemensg/passenger,kewaunited/passenger,kewaunited/passenger,cgvarela/passenger,antek-drzewiecki/passenger,kewaunited/passenger,clemensg/passenger,clemensg/passenger,clemensg/passenger,antek-drzewiecki/passenger,kewaunited/passenger,cgvarela/passenger,cgvarela/passenger,phusion/passenger,kewaunited/passenger,phusion/passenger,cgvarela/passenger,cgvarela/passenger,clemensg/passenger,antek-drzewiecki/passenger,antek-drzewiecki/passenger,phusion/passenger,clemensg/passenger,antek-drzewiecki/passenger,cgvarela/passenger,phusion/passenger,phusion/passenger,kewaunited/passenger,phusion/passenger,kewaunited/passenger,cgvarela/passenger,clemensg/passenger,antek-drzewiecki/passenger,phusion/passenger,kewaunited/passenger,cgvarela/passenger,antek-drzewiecki/passenger,antek-drzewiecki/passenger