Fix incremental linking setting for Fortran + VS

This commit fixes a bug where it was impossible to specify
/INCREMENTAL to Fortran projects built with Visual Studio.

The problem was due to the fact that .vfproj files expect
the value of this flag to be "linkIncremental{No,Yes},
whereas .vcproj files expect this value to be 0, 1, or 2.

The implementation of this fix adds a new data structure for
Visual Studio linker flags specific to Fortran.  This can
easily be extended in the future if more such discrepencies
between C/C++ and Fortran linking are discovered.
Merge topic 'fortran-linker-flags' into next

17b0fe03 Fix incremental linking setting for Fortran + VS