util.cc: Reusing windows workaround for cygwin.

This fixes:
src/util.cc: In function 'double GetLoadAverage()':
src/util.cc:337:28: error: 'getloadavg' was not declared in this scope
Merge pull request #498 from pck/cygwin

util.cc: Reusing windows workaround for cygwin.
add syntax for checking versions
docs for ninja_required_version

(And some extra docs for top-level variables in general.)
depfile helper: check errors on writing .d files

Closes #492 and #493.
say where the default value for -j comes from

This is a FAQ.
move from asciidoc html to asciidoc -> docbook -> html

As best as I can tell this is the easiest way to customize
the asciidoc HTML output.
rearrange env variable section layout
Fix typo in manual
make doc xrefs link to section headers
add versioning notes to features in the manual

This helps guide which ninja version to depend on.
manual: move in_newline to the reference

It's a detail, it doesn't belong in the brief tutorial overview.
Removed unused UnitsWaiting() function from State class.

This function was added at 307f0bbd("and some basic implementation"), but nobody
calls it anymore.

Signed-off-by: Thiago Farina <tfarina@chromium.org>
Fix typo, s/verison/version/
Add a check for the VC++ 2012-style 64-bit path.
In VS2012 the path to the 64-bit tools has changed to
VCINSTALLDIR\bin\x86_amd64\cl.exe. This change will make the bootstrap
check there to see if it exists before falling back to the old amd64 path.
Fix wrong usage of std::string::find
Merge pull request #506 from syntheticpp/string-find

Fix wrong usage of std::string::find
Browse command does not parse URL correctly
Merge pull request #502 from tfarina/rm-unused-fun

Removed unused UnitsWaiting() function from State class.
Merge pull request #507 from ikarienator/master

Browse command does not parse URL correctly