Escape < and & in SGML
This is not required in SGML, but will be in XML, so this is a step to
prepare for the conversion to XML. (It is still not required to escape
>, but we did it here in some cases for symmetry.)
Add a command-line option to osx/onsgmls calls to warn about unescaped
occurrences in the future.
Author: Alexander Law <exclusion@gmail.com>
Author: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>