.EM found missing

[Dorai Sitaram]

UTP strongly hints that the -ms macros have the end-of-input trap .em pre-set 
to a defined macro called .EM, with the implication that if the user wants to 
affect end-of-input behavior they can append or prepend to this macro rather 
than messing with .em directly. However groff's s.tmac sets its .em value to a 
macro of another name (viz., .pg@end-text).

This is probably one place where one can safely bring back compatibility to 
earlier times.  It is not necessary to give up .pg@end-text: .EM could either 
expand to or be an alias to .pg@end-text.  I can't think of any  modernizing 
rationale for groff to give up this convention. FWIW, both Heirloom and 
neatroff keep the .EM.

--d