Experimental Fortran 2018 compiler (20180108)

This release is based on the Sourcery Institute GCC fork's teams branch with commits from the GCC git mirror through 8 January 2018 and commits unique to the teams branch through 18 December 2017. With the additional support this branch provides for teams, gfortran is approaching full compliance with the Fortran 2018 Draft International Standard, notwithstanding bugs, some partially supported major features, and a few unsupported minor features.