This fixes a test (formatfiltertest07) failure on i686-linux.
See also <https://github.com/steveire/grantlee/issues/85>.
* gnu/packages/patches/grantlee-fix-i586-precision.patch: New file.
* gnu/local.mk (dist_patch_DATA): Register it.
* gnu/packages/qt.scm (grantlee)[source]: Add patch.
