doc: Review and update documentation for "Matrix Manipulation" chapter. * matrix.txi, arrayfun.m, blkdiag.m, fliplr.m, flipud.m, logspace.m, postpad.m, prepad.m, randi.m, repmat.m, rot90.m, rotdim.m, shiftdim.m, sortrows.m, vech.m, xor.m, hadamard.m, hankel.m, hilb.m, invhilb.m, magic.m, pascal.m, rosser.m, sylvester_matrix.m, toeplitz.m, vander.m, wilkinson.m, bsxfun.cc, find.cc, lookup.cc, rand.cc, tril.cc, data.cc, arrayfun.m, blkdiag.m, fliplr.m, flipud.m, logspace.m, postpad.m, prepad.m, randi.m, repmat.m, rot90.m, rotdim.m, shiftdim.m, sortrows.m, vech.m, xor.m, hadamard.m, hankel.m, hilb.m, invhilb.m, magic.m, pascal.m, rosser.m, sylvester_matrix.m, toeplitz.m, vander.m, wilkinson.m, bsxfun.cc (bsxfun), find.cc (find), lookup.cc (lookup), rand.cc (rand, randn, rande, randg, randp), tril.cc (triu), data.cc (all, any, horzcat, vertcat, cat, permute, ipermute, ones, zeros, eye, linspace, resize, reshape, issorted, diff): Improve docstrings

--- a/scripts/general/flipud.m
+++ b/scripts/general/flipud.m
@@ -18,7 +18,8 @@
 
 ## -*- texinfo -*-
 ## @deftypefn {Function File} {} flipud (@var{x})
-## Return a copy of @var{x} with the order of the rows reversed.  For
+## Return a copy of @var{x} with the order of the rows reversed.  In
+## other words, @var{x} is flipped upside-down about a horizontal axis.  For
 ## example:
 ##
 ## @example
@@ -29,8 +30,7 @@
 ## @end group
 ## @end example
 ##
-## Due to the difficulty of defining which axis about which to flip the
-## matrix @code{flipud} only work with 2-d arrays.  To flip N-d arrays
+## Note that @code{flipud} only works with 2-D arrays.  To flip N-D arrays
 ## use @code{flipdim} instead.
 ## @seealso{fliplr, flipdim, rot90, rotdim}
 ## @end deftypefn