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/path/pathdef.m
+++ b/scripts/path/pathdef.m
@@ -76,7 +76,7 @@
 
 endfunction
 
-## Extact the path information from the script/function @var{file}, created by
+## Extract the path information from the script/function @var{file}, created by
 ## @file{savepath.m}.  If successful, @code{__extractpath__} returns the path
 ## specified in @var{file}.