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/statistics/distributions/stdnormal_pdf.m
+++ b/scripts/statistics/distributions/stdnormal_pdf.m
@@ -47,10 +47,10 @@
 %! y = 1/sqrt(2*pi)*exp (-x.^2/2);
 %!assert (stdnormal_pdf ([x, NaN]), [y, NaN], eps)
 
-%% Test class of input preserved
+## Test class of input preserved
 %!assert (stdnormal_pdf (single ([x, NaN])), single ([y, NaN]), eps ("single"))
 
-%% Test input validation
+## Test input validation
 %!error stdnormal_pdf ()
 %!error stdnormal_pdf (1,2)
 %!error stdnormal_pdf (i)