Consistency: "{\bf ...}" ==> "\strong{...}"

"{\em ...}" ==> "\emph{...}"

	      Not at all sure what to do with "{\rm ...}".
	      Leaving it for now.

Doc/lib/libgl.tex

@@ -3,7 +3,7 @@
 \bimodindex{gl}
 
 This module provides access to the Silicon Graphics
-{\em Graphics Library}.
+\emph{Graphics Library}.
 It is available only on Silicon Graphics machines.
 
 \strong{Warning:}
@@ -191,7 +191,7 @@ main()
 \stmodindex{DEVICE}
 
 These modules define the constants used by the Silicon Graphics
-{\em Graphics Library}
+\emph{Graphics Library}
 that C programmers find in the header files
 \file{<gl/gl.h>}
 and