http://sources.redhat.com/automake/automake.html#Extending-aclocal documents
that starting with Automake 1.8, aclocal will warn about all underquoted calls
to AC_DEFUN due to the fact that in a single aclocal run it might include more
than once all .m4 files which it finds available, this includes .m4 files from
other software packages.

If the first argument to AC_DEFUN is underquoted and the same macro is included
more than once, successive inclusions after the first one will expand the macro
instead of assuming it is the same as the first one included.

needed, and being able to define it if appropriate for further configure tests
as well as for the generated config file.

Introduced reentrant.m4 intended for our reentrant related autotools/m4 macros.

lines ending in \r.

defined by the libcurl API. Also changed curl_easy_setopt examples to
pass longs where appropriate.

  non-zero with the fixed value of 1. We should strive at making options
  support '1' for enabling them mentioned explicitly, as that then will allow
  us for to extend them in the future without breaking older programs.

actually verify if the test is properly working

setting as the one actually used when finally building the library.

checks for gethostbyname_r with 5 and 6 args now also done with -D_REENTRANT

data type for systems where this sixth argument is prototyped as a void pointer.

Start of thread: http://curl.haxx.se/mail/lib-2008-07/0153.html

now cause the definition of RECVFROM_TYPE_ARG2_IS_VOID, RECVFROM_TYPE_ARG5_IS_VOID
or RECVFROM_TYPE_ARG6_IS_VOID, as appropriate.

failure to properly detect recvfrom arg types on Solaris

function recvfrom as a result of the info additionally logged when running on a
Solaris system.

The compiler error showed that the prototype being used on Solaris was the one
declared in line 427 of "/usr/include/sys/socket.h" as:

function(int,
         pointer to void,
         unsigned int,
         int,
         pointer to struct sockaddr,
         pointer to void) returning int

failure to properly detect recvfrom arg types on Solaris

to the data type pointed by its respective argument and not the pointer type.

finds out its return type and the types of its arguments. Added definitions
for non-configure systems config files, and introduced macro sreadfrom which
will be used on udp sockets as a recvfrom() wrapper.

Configure process no longer needs nor checks size of curl_off_t.
Library will now be built with _REENTRANT symbol defined.