GCN libgfortran.

GCN libgfortran.

This patch contains the GCN port of libgfortran.  We use the minimal
configuration created for NVPTX.  That's all that's required, besides the
target-independent bug fixes posted already.

2019-01-17  Andrew Stubbs  <ams@codesourcery.com>
	    Kwok Cheung Yeung  <kcy@codesourcery.com>
	    Julian Brown  <julian@codesourcery.com>
	    Tom de Vries  <tom@codesourcery.com>

	libgfortran/
	* configure.ac: Use minimal mode for amdgcn.
	* configure: Regenerate.

Co-Authored-By: Julian Brown <julian@codesourcery.com>
Co-Authored-By: Kwok Cheung Yeung <kcy@codesourcery.com>
Co-Authored-By: Tom de Vries <tom@codesourcery.com>
From-SVN: r268020