* build-aux/freeimageplus.m4: New.
	Provide the Autoconf macro OLN_WITH_FREEIMAGEPLUS.
	Inspired by Olena 0.11's macros AC_WITH_CXX_ZLIB and
	AC_WITH_CXX_FFTW.
	Use this macro...
	* configure.ac: ...here, instead of the previous ad hoc solution.
	Rename the Automake conditional FREE_IMAGE_PLUS as FREEIMAGEPLUS,
	and adjust it.
	* Makefile.am (ACLOCAL_AMFLAGS): New.
	Set it to `-I build-aux' to have aclocal visit
	build-aux/freeimageplus.m4.


git-svn-id: https://svn.lrde.epita.fr/svn/oln/trunk@1409 4aad255d-cdde-0310-9447-f3009e2ae8c0