doc: Spellcheck documentation ahead of 4.4 release. * aspell-octave.en.pws: Add new words to Octave-only spelling dictionary. Remove exception words which are no longer used in manual. * basics.txi, bugs.txi, func.txi, geometry.txi, install.txi, matrix.txi, package.txi, plot.txi, poly.txi, preface.txi, quad.txi, sparse.txi, strings.txi, vectorize.txi, data.cc, defaults.cc, file-io.cc, pinv.cc, quadcc.cc, qz.cc, rand.cc, schur.cc, syscalls.cc, sysdep.cc, toplev.cc, amd.cc, audioread.cc, colamd.cc, dmperm.cc, symrcm.cc, quadgk.m, quadl.m, imfinfo.m, rgb2gray.m, javachk.m, usejava.m, unpack.m, fzero.m, glpk.m, pqpnonneg.m, stemleaf.m, print.m, polyfit.m, blackman.m, bicgstab.m, cgs.m, eigs.m, pcg.m, tfqmr.m, gallery.m, rosser.m, toeplitz.m, vander.m, isstrprop.m: Add @nospell{} macro around proper names and other words which aspell should not check. Correct misspellings identified by aspell.

--- a/libinterp/dldfcn/symrcm.cc	Mon Mar 26 22:54:24 2018 +0200
+++ b/libinterp/dldfcn/symrcm.cc	Mon Mar 26 10:45:04 2018 -0700
@@ -433,7 +433,7 @@
 in
 
 @nospell{E. Cuthill, J. McKee}. @cite{Reducing the Bandwidth of Sparse
-Symmetric Matrices}. Proceedings of the 24th ACM National Conference,
+Symmetric Matrices}. Proceedings of the 24th @nospell{ACM} National Conference,
 157--172 1969, Brandon Press, New Jersey.
 
 @nospell{A. George, J.W.H. Liu}. @cite{Computer Solution of Large Sparse