based on the 'visibility' attribute for GNUC and __global for Sun
compilers, taking also in account __declspec function decoration
for Win32 and Symbian DLL's.

Introducing configure options --enable-hidden-symbols and
--disable-hidden-symbols following libcurl's naming.

ARES_ECANCELLED error code value and missing error code description.

is only expanded and included once in the configure script.

due to autoconf 2.64 m4_require'ing it in _AS_SHELL_SANITIZE indirectly through
_AS_PATH_WALK.

Fix potential out-of-bounds read

Fix compiler warning: loop without body

- Fixing out of bounds memory overwrite triggered with malformed /etc/hosts file.
- Improving parsing of /etc/hosts file.
- Validating requested address family.
- Ensuring that failures always return a NULL pointer.
- Adjusting header inclusions.

make errno available as a preprocessor macro.

changed u_int16_t to unsigned short because it is the only place within ares and curl where such a type would be used;
also it broke many autobuilds. We should probably introduce an ares_port_t if we want to use a type here.

Added 'ares_parse_srv_reply.obj'. Added definition of 'u_int16_t'. This is I don't like; we should not depend on such non-universal types in a public header. But this is just a quick fix.

Support lookup of IPv4 literals in ares_gethostbyname(), even when the address family is set to AF_INET6.

  ares_cancel() is used, to be ARES_ECANCELLED instead of ARES_ETIMEOUT to
  better allow the callback to know what's happening.

  fails to get inited by other means. This fixes a case of when the c-ares
  init fails when internet access is fone.

renamed generated config.h to ares_config.h in order to avoid clashes when libcurl is used with other projects which also have a config.h.