Give ESI subrequests a ReqAcct.

Make the bodycount in ReqAcct only the actual body, not including
transmission overhead (such as chunked encoding)

already in the l%d log records

to reflect changes from c74bd5f8

Here we insist the file is completely allocated

This function makes sure that the filesystem can accomodate the file
of the given size.

Checks the filesystem free space up against the allocated blocks as a
sanity check.

Uses fallocate if available to preallocate the needed blocks.

If fallocate isn't available, it will write zero bytes if insist is true.

system size

This is to spot obvious typos