xlf95 does not accept "-D" from autoconf

[Christoffer Hirth]

I'm currently working on porting the build script of a fortran library
to autotools.
This library will be run on multiple configurations, ranging from
regular desktop to cray supercomputers.

However on machines using IBM's fortran compiler (xlf90 or 95)
compilation fails due to unsupported defined variables "-DPACKAGENAME"
etc.
On ibm this should be passed as -WF,-DPACKAGENAME.

How can I modify autotools behaviour, or simply skip these definitions
(they are not used)?


-- Christoffer