Adding license
Got doxygen to work finally.
The script was downloaded from

http://www.gnu.org/software/autoconf-archive/ax_prog_doxygen.html

Be careful with missing tabs in aminclude.am on these lines
when copying the script. The result was that Makefile was
giving me ** missing separator error

@DX_DOCDIR@/@PACKAGE@.tag: $(DX_CONFIG) $(pkginclude_HEADERS)
    rm -rf @DX_DOCDIR@
    $(DX_ENV) $(DX_DOXYGEN) $(srcdir)/$(DX_CONFIG)