Rewrite page(2) references to page(3).

Add description of new libmach.

man/man3/draw.3

@@ -261,7 +261,7 @@ number of bits per pixel in the picture;
 it is identically
 .B chantodepth(chan)
 (see
-.IR graphics (2))
+.IR graphics (3))
 and is provided as a convenience.
 The value should not be modified after the image is created.
 .TP
@@ -705,7 +705,7 @@ what
 is to
 .B atan
 (see
-.IR sin (2)).
+.IR sin (3)).
 .TP
 .BI border( dst\fP,\fP\ r\fP,\fP\ i\fP,\fP\ color\fP,\fP\ sp\fP)
 .I Border
@@ -803,11 +803,11 @@ is non-zero.
 .SH SOURCE
 .B /sys/src/libdraw
 .SH SEE ALSO
-.IR graphics (2),
-.IR stringsize (2),
+.IR graphics (3),
+.IR stringsize (3),
 .IR color (6),
 .IR utf (6),
-.IR addpt (2)
+.IR addpt (3)
 .PP
 T. Porter, T. Duff.
 ``Compositing Digital Images'',