Allow select()ing up to 1024 file descriptors on Windows
fix !O_NONBLOCK where ~O_NONBLOCK was meant

Using ! on a non-zero value will always return 0.

Also remove some duplicate and superfluous code in other places.
Print actual Win32 error that occurred on file creation failure.
Checking whether closing succeeds
Allow files to be opened for reading multiple times
Try to increase file descriptor rlimit if necessary

As the default can be too low, especially on OSX.
Merge pull request #2569 from sipa/win1024fd

Allow select()ing up to 1024 file descriptors on Windows
Accept negative -par values to leave N CPUs free.
Merge pull request #2349 from dserrano5/master

Accept negative -par values to leave N CPUs free.
Merge pull request #2568 from sipa/rlimit

Try to increase file descriptor rlimit if necessary
Merge pull request #2589 from sipa/win32ldberr

Some win32-leveldb related fixes
Merge pull request #2583 from laanwj/2013_04_netbase_bitfield

netbase: fix !O_NONBLOCK where ~O_NONBLOCK was meant