AC_PROG_CXX, AC_PROG_CXXCPP, AC_REQUIRE_CPP
for checking both C++ and C features in one configure script.
* New macros AC_CHECKING, AC_VERBOSE, AC_WARN, AC_ERROR for printing messages.
-* New macros AC_FIND_XTRA, AC_MMAP.
+* New macros AC_FIND_XTRA, AC_MMAP, AC_SIZEOF_TYPE.
* AC_FIND_X looks for X in more places.
* AC_PROG_INSTALL defaults to install.sh instead of cp, if it's in srcdir.
install.sh is distributed with Autoconf.