it fails if the macro that is being undefined is not already defined. To
make this work under all cases and be sure that at a certain point some
specific macro isn't defined we must use the following style in configure:

m4_ifdef([macro], [m4_undefine([macro])])

Luckily, they weren't needed.

Added -DHAVE_STRUCT_TIMEVAL to CFLAGS.

since it's already included through "setup.h".

Check for lowercase 'bool' type at configuration stage. If not available
provide a suitable replacement with a type definition of 'unsigned char'
in setup_once.h

Move definitions of TRUE and FALSE to setup_once.h

struct for platforms that don't have it to setup_once.h

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"

macro to provide this functionality on all platforms

provide a suitable replacement for use in our ISBLANK macro

DNS from /etc/nsswitch.conf, /etc/host.conf or /etc/svc.conf when
/etc/resolv.conf did not exist or was unable to read it.

*) Update CURL_CC_DEBUG_OPTS from curl's script