h2load has supported uploading a file quite a while, but it turns out
that it worked with HTTP/2 and SPDY only. HTTP/1 with upload did not
work. This commit fixes this bug, and implement HTTP/1 upload. Due
to architectural limitation of h2load, when -d option is used, the
number of in-flight pipe-lined requests is set to 1.
From autoconf manual, section 5.6.1 Portability of Headers, says:
"""
The C99 standard says that inttypes.h includes stdint.h, so there's no
need to include stdint.h separately in a standard environment. Some
implementations have inttypes.h but not stdint.h (e.g., Solaris 7),
but we don't know of any implementation that has stdint.h but not
inttypes.h.
"""