Merge branch 'po/hash-object-size-t' into jch

Merge branch 'po/hash-object-size-t' into jch

Support for hashing loose or packed objects larger than 4GB on Windows
and other LLP64 platforms has been improved by converting object header
buffers and data-handling functions from 'unsigned long' to 'size_t'.

* po/hash-object-size-t:
  hash-object: add a >4GB/LLP64 test case using filtered input
  hash-object: add another >4GB/LLP64 test case
  hash-object --stdin: verify that it works with >4GB/LLP64
  hash algorithms: use size_t for section lengths
  object-file.c: use size_t for header lengths
  hash-object: demonstrate a >4GB/LLP64 problem