Dispatch IO: Request a smaller buffer if valloc() fails
Dispatch IO: Request a smaller buffer if valloc() fails

I had some issues with this happening on my 32-bit Ubuntu VM, which only has 768MB memory allocated.

nickhutchinson/libdispatch,SproutOrc/libdispatch,evaautomation/libdispatch,SproutOrc/libdispatch,PSPDFKit-labs/libdispatch,evaautomation/libdispatch,nickhutchinson/libdispatch,nickhutchinson/libdispatch,PSPDFKit-labs/libdispatch,PSPDFKit-labs/libdispatch,SproutOrc/libdispatch,PSPDFKit-labs/libdispatch,SproutOrc/libdispatch,nickhutchinson/libdispatch,evaautomation/libdispatch,evaautomation/libdispatch