I have an XSL-FO file (actually, many such files) using FreeSerif.  (I've
attached an example to this report.)  This XSL-FO file doesn't use
italics at all.

If I have `fonts-freefont-ttf` but _not_ `fonts-freefont-otf` installed
then the body text renders as roman (that is, not italic).  However, if
I have the latter installed, the body text is italic.  Obviously, this
is unwanted, since the real body text is supposed to be in roman text.
Note that if the XSL-FO file _does_ contain italics, the text is also in
italics then, too.

It's unclear to me whether this is a bug in FOP or elsewhere, so please
feel free to reassign if need be.  Also, if you need additional example
XSL-FO files or toolchain commands to generate them, please let me know.