AC_caolan_SEARCH_PACKAGE(PACKAGE, FUNCTION, LIBRARY LIST, HEADERFILE [, ACTION-IF-FOUND [, ACTION-IF-NOT-FOUND]])

This searchs for a package by looking in the LIBRARY LIST for the FUNCTION, and 
searching for the HEADERFILE. It causes configure to have extra command line
options of 
--with-PACKAGE[=DIR]
--without-PACKAGE
--with-PACKAGE-include=DIR
--with-PACKAGE-libdir=DIR
So that either the currently common mechanism of specifying the root dir of
an include and lib pair can be used as well as specifiying the exact paths
for where the header and library files can be found.

configure can put its headers and libraries into seperate locations with
--includedir --libdir so it should be easy to setup a package with configure
which can compile against a package seperated like this. Use of AC_SEARCH_PACKAGE
makes this trivial.

C.