--enable-tex option seems to fix staggered multi-shift K20 issues

updated README and added this option to configure.milc.titan
Only bind gauge and clover fields if we have to.
Fixed typo in ifdef TEXTURE_OBJECT .
Texture objects are now always used on Kepler, irrespective of the
configure option
Removed "--enable-tex-object" option from configure.ac (configure not
yet regenerated).
Regenerated configure script with autoconf 2.68 (removing
"--enable-tex-object" option)
Fixed another #ifdef/#if bug
Added support for texture objects in gauge field and clover field.  Enabled the use of these in all dslash kernels.
Added spinor support for texture objects in all dslash kernels.
Added comments to coordsFromIndex

Ron has implemented some nice lattice site indexing functions.
The logic behind the indexing functions is pretty neat, but
a little too opaque for me. I've added a comment to one
of the functions to clarify what's going on.
Added texture object support to packing kernels.
Removed struct redefine warning.
Merge branch 'master' into tex_object

Conflicts:
	lib/dslash_textures.h
Fixed macro bug for texture objects.
Merge branch 'master' into tex_object
Updated TEXTURE_OBJECT to USE_TEXTURE_OBJECTS throughout the library.
Fixes to linux compilation and when texture objects are disabled.
When using texture references, always bind and unbind, else half precision breaks.  Fixed bug with long link texture binding.
Fixed memory leak in unitarize_link_test.
Added fix for fat-link kernels (which still use tex references) when texture objects are enabled.