document building against r2338
psol: support a binary distribution

We want people to be able to install ngx_pagespeed like any other nginx module.
If PSOL were a full-fledged library with a stable interface we could simply say
"install PSOL" which might be as easy as `apt-get install psol-dev`, but it's
not.  Instead we directly include a precompiled binary library along with its
headers.  By building the binaries on something sufficiently old (Centos 5.4)
they should work pretty much everywhere someone might think to run
ngx_pagespeed, but building from source is still a documented option if they
don't.

Headers and binaries are from trunk of r2338, as documented in the READMEs.
Merge pull request #6 from yaoweibin/junmin-ngx-url-async-fetcher

fixed some comment and coding style
base fetch: fix two memory leaks, one severe and one potential
Merge pull request #121 from pagespeed/jefftk-leak

base fetch: fix two memory leaks, one severe and one potential
options: don't leak custom options
Merge pull request #123 from pagespeed/jefftk-leak

options: don't leak custom options
Merge pull request #119 from pagespeed/jefftk-binary-psol

psol: support a binary distribution
readme: svn commands need to be run under src/
Merge branch 'master' of github.com:pagespeed/ngx_pagespeed
readme: be consistent with debug usage
options: delete on process exit
document testing with valgrind
Merge pull request #124 from pagespeed/jefftk-leak

options: delete on process exit
readme: put valgrind doc in the right section of the config
remove stray fi
readme: run configure from nginx/ not nginx/src/
Revert "filecache-worker: hook the worker up to the filecache"

This is causing segfaults on jefftk.com.

This reverts commit 6f927897ec7917939399f1a508499bd6ad47c18d.
load-from-file: port load-from-file

load-from-file is helpful in may setups, and also is used in many
vhosts in the test configuration

Squash-merge of Otto's change via pull request #125
threads: CHECK-fail on threads started before forking