maint: Clean up m-files to follow Octave coding conventions. Try to trim long lines to < 80 chars. Use '##' for single line comments. Use '(...)' around tests for if/elseif/switch/while. Abut cell indexing operator '{' next to variable. Abut array indexing operator '(' next to variable. Use space between negation operator '!' and following expression. Use two newlines between endfunction and start of %!test or %!demo code. Remove unnecessary parens grouping between short-circuit operators. Remove stray extra spaces (typos) between variables and assignment operators. Remove stray extra spaces from ends of lines.

--- a/scripts/general/blkdiag.m
+++ b/scripts/general/blkdiag.m
@@ -76,7 +76,7 @@
 ## tests involving sparse matrices
 %!assert (blkdiag (sparse ([1,2;3,4]),[5,6;7,8]), sparse ([1,2,0,0;3,4,0,0;0,0,5,6;0,0,7,8]))
 %!assert (blkdiag (sparse ([1,2;3,4]),[5,6]), sparse ([1,2,0,0;3,4,0,0;0,0,5,6]))
-# sanity checks
+## sanity checks
 %!test
 %! A = rand (round (rand (1, 2) * 10));
 %! assert (blkdiag (A), A);