doc: Periodic grammarcheck of documentation. * doc/interpreter/basics.txi, doc/interpreter/container.txi, doc/interpreter/contrib.txi, doc/interpreter/diagperm.txi, doc/interpreter/errors.txi, doc/interpreter/install.txi, doc/interpreter/sparse.txi, libinterp/corefcn/ellipj.cc, libinterp/corefcn/mappers.cc, libinterp/corefcn/regexp.cc, libinterp/corefcn/tril.cc, libinterp/dldfcn/__init_fltk__.cc, libinterp/dldfcn/fftw.cc, libinterp/interpfcn/dirfns.cc, libinterp/interpfcn/input.cc, libinterp/octave-value/ov-fcn-inline.cc, libinterp/octave-value/ov-struct.cc, scripts/@ftp/cd.m, scripts/general/interp1.m, scripts/general/num2str.m, scripts/image/ind2rgb.m, scripts/image/rgb2ind.m, scripts/io/importdata.m, scripts/io/textread.m, scripts/java/javamem.m, scripts/linear-algebra/condest.m, scripts/linear-algebra/onenormest.m, scripts/miscellaneous/error_ids.m, scripts/miscellaneous/getfield.m, scripts/miscellaneous/setfield.m, scripts/plot/area.m, scripts/plot/pcolor.m, scripts/plot/stairs.m, scripts/set/powerset.m, scripts/sparse/bicg.m, scripts/sparse/bicgstab.m, scripts/sparse/cgs.m, scripts/specfun/ellipke.m, scripts/special-matrix/gallery.m, scripts/strings/strjoin.m, scripts/strings/strsplit.m, scripts/testfun/__have_feature__.m, scripts/testfun/__printf_assert__.m, scripts/testfun/__prog_output_assert__.m, scripts/testfun/__run_test_suite__.m: grammarcheck documentation.