maint: Use "fcn" as preferred abbreviation for "function" in libinterp/. * __eigs__.cc, bsxfun.cc, cellfun.cc, daspk.cc, dasrt.cc, dassl.cc, data.cc, debug.cc, error.cc, graphics.cc, graphics.in.h, gzfstream.h, ls-hdf5.cc, lsode.cc, max.cc, oct-opengl.h, quad.cc, strfns.cc, utils.cc, utils.h, variables.cc, __ode15__.cc, gzip.cc, cdef-manager.cc, ov-fcn-handle.cc, ov-java.cc, ov-usr-fcn.cc, bp-table.cc, bp-table.h, lex.h, lex.ll, oct-parse.yy, pt-eval.cc: Replace "func", "fun", "fn" in documentation and variable names with "fcn".

((nil .
      ((c-file-style . "gnu")
       (indent-tabs-mode . nil)
       (fill-column . 72)))
 (change-log-mode . ((indent-tabs-mode . t)))
 (makefile-mode . ((indent-tabs-mode . t))))