Do not talk about "real" numbers; talk about "floats" or "floating point

numbers" instead; we have not described "reals" anywhere else in the
documentation, and this is not the place to change the story!

Reported by Keith Briggs <keith.briggs@bt.com>.

Doc/lib/libmath.tex

@@ -36,7 +36,7 @@ Return \code{atan(\var{y} / \var{x})}.
 \end{funcdesc}
 
 \begin{funcdesc}{ceil}{x}
-Return the ceiling of \var{x} as a real.
+Return the ceiling of \var{x} as a float.
 \end{funcdesc}
 
 \begin{funcdesc}{cos}{x}
@@ -52,11 +52,11 @@ Return \code{e**\var{x}}.
 \end{funcdesc}
 
 \begin{funcdesc}{fabs}{x}
-Return the absolute value of the real \var{x}.
+Return the absolute value of the floating point number \var{x}.
 \end{funcdesc}
 
 \begin{funcdesc}{floor}{x}
-Return the floor of \var{x} as a real.
+Return the floor of \var{x} as a float.
 \end{funcdesc}
 
 \begin{funcdesc}{fmod}{x, y}
@@ -92,7 +92,7 @@ Return the base-10 logarithm of \var{x}.
 
 \begin{funcdesc}{modf}{x}
 Return the fractional and integer parts of \var{x}.  Both results
-carry the sign of \var{x}.  The integer part is returned as a real.
+carry the sign of \var{x}.  The integer part is returned as a float.
 \end{funcdesc}
 
 \begin{funcdesc}{pow}{x, y}