Ctrl-' will render the straight apostrophe manually, instead of the curly apostrophe, but I know of no way to turn off smart quotes for apostrophes only. Turning off smart quotes affects both single and double quotes, and apostrophes. Perhaps you could redefine what constitutes a smart quote in maker.ini, by substituting an \x27 value for \xd5. Of course, that will also mean no smart right single quotes. Here is the appropriate section of maker.ini that you would change:
; Smart Quote Characters ; SmartQuotes \xd4\xd5\xd2\xd3 ) English curved quotes ; SmartQuotes \xe2\xd4\xe3\xd2 ) German-style quotes with base quotes ; SmartQuotes \xd5\xd5\xc7\xc8 ) French-style quotes using guillemets ; SmartQuotes \xd5\xd5\xd3\xd3 ) Swedish- and Finnish-style quotes ; SmartQuotes \xd4\xd5\xd2\xd3 ) Italian curved quotes ; ; English curved quotes: SmartQuotes=????
