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

This check never worked as intended for several reasons:

- Didn't take the existing file size into account, causing it to
  succeed on first startup but fail on next

- Sparse files were not handled, and can't be handled as we don't know
  where in the file a hole could be and whether truncation actually
  would change the number of blocks used at all

Fixes: #1343

Fixes #1612
Testcase by: 	daghf