Switch from adaptive pthread mutexes by default, based on:

http://smalldatum.blogspot.com/2014/08/the-innodb-mutex.html

There's more information here:

http://stackoverflow.com/questions/19863734/what-is-pthread-mutex-adaptive-np

Add a new option, --pthread_adaptive to configure adaptive mutexes.

Don't list --pthread-logging in the --with-spinlock=XXX configure usage
message, that's not for public use.

Add a tuning page that talks about mutex choice.
whitespace
Linux adaptive pthread mutexes are less interesting for condition
variables, they're expected to block so there's no reason to spin
hoping the lock becomes available.
Fix ifdef for adaptive mutexes.
Fix log_filesize calculation. #1106
My change broke ex_log.  Back out change until I figure it out.
Use WT_PAGE_IS_INTERNAL instead of testing explicitly.
whitespace
KNF
whitespace
whitespace
Don't re-compile the RE on every loop.