Major Update. Macro files now stored internally.
LIB_f90 used to read macro files on the fly, branching into a new macro
meant that the new file was read from disk again once the inner macro
was finished, creating a lot of unnecessary I/O.
Open topic at the moment: If a macro file is modified on the disk it is
not updated internally. "fstat" is not fortran standard, would not work
on intel/prortland/etc  compilers