the multi interface and connection re-use that could make a
  curl_multi_remove_handle() ruin a pointer in another handle.

  The second problem was less of an actual problem but more of minor quirk:
  the re-using of connections wasn't properly checking if the connection was
  marked for closure.

linked to the networking libraries.

and those required by other components to avoid forcing unneeded
dependencies into the target objects.

  CURLOPT_RANGE back to no range on an easy handle when using FTP.

making them available to any source code file which includes "setup.h".

Macro SOCKERRNO / SET_SOCKERRNO() returns / sets the *socket-related* errno
(or equivalent) on this platform to hide platform details to code using it.

Macro ERRNO / SET_ERRNO() returns / sets the NOT *socket-related* errno
(or equivalent) on this platform to hide platform details to code using it.

FD_ISSET, and FD_ZERO macros emits warnings #1469 and #593.
So for icc 9.0 we also ignore warnings #1469 and #593.
* 593 warns on "variable __d0 was set but never used"
* 1469 warns on "cc clobber ignored"

build targets when --disable-verbose is specified.

macro to provide this functionality on all platforms

dependencies to applications.

retrying upon EINTR errors.