defining HAVE_SIGNAL_H if the header is available.

Added a check in configure that tests if the sig_atomic_t type is
available, defining HAVE_SIG_ATOMIC_T if it is available. Providing
a suitable default in setup_once.h if not available.

Added a check in configure that tests if the sig_atomic_t type is
already defined as volatile, defining HAVE_SIG_ATOMIC_T_VOLATILE
if it is available and already defined as volatile.

cross-compiling) in order to detect problems with run-time libraries that
otherwise would occur when the sizeof tests for curl_off_t would run and
thus be much more confusing to users. The check of course should run after
all lib-checks are done and before any other test is used that would run an
executable built for testing-purposes.

Reintroduce checking for HAVE_MSG_NOSIGNAL in configure script, so that we don't depend on header inclusion order for a valid check.

file: URLs only.

Define NEED_MALLOC_H if including <stdlib.h> is not enough for proper compilation and <malloc.h> must also be included.

-fvisibility=hidden on gcc >= 4.0.  This reduces the size of the libcurl
binary and speeds up dynamic linking by hiding all the internal symbols from
the symbol table.

script to fail on debian unstable (some specific bash version perhaps?)

AC_CHECK_HEADERS() and the action-if-found since that action is run even if
just one of the six headers is found and I just now fell over a case with
a duplicate file name (a krb4 implementation with an err.h file).

I converted the check to manually make sure three of the headers are present
before considering them fine.

arguments work properly - and the option is not harmful for the rest of the
curl build either!

fork support for cooler tests

instead of LDFLAGS.

not supporting it. It hasn't been functioning for years anyway, so this is
just finally stating what already was true. And a cleanup at the same time.

done in one single function CURL_CHECK_FUNC_GETNAMEINFO which
will only define HAVE_GETNAMEINFO if the function has been found
AND the type of its arguments has been properly been detected

CURL_FUNC_GETNAMEINFO_ARGTYPES now also checks first argument.
All related changes taken to cares configuration scripts.

valid windows.h winsock.h winsock2.h and ws2tcpip.h
header files:
CURL_CHECK_HEADER_WINDOWS
CURL_CHECK_HEADER_WINSOCK
CURL_CHECK_HEADER_WINSOCK2
CURL_CHECK_HEADER_WS2TCPIP