sync code with last improvements from OpenBSD

doc/gl-docs/GLU/ortho2d.3gl

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+'\" e
+'\"! eqn | mmdoc
+'\"macro stdmacro
+.ds Vn Version 1.2
+.ds Dt 6 March 1997
+.ds Re Release 1.2.0
+.ds Dp May 02 11:53
+.ds Dm 37 ortho2d.g
+.ds Xs 62574 3 ortho2d.gl
+.TH GLUORTHO2D 3G
+.SH NAME
+.B "gluOrtho2D
+\- define a 2D orthographic projection matrix
+
+.SH C SPECIFICATION
+void \f3gluOrtho2D\fP(
+GLdouble \fIleft\fP,
+.nf
+.ta \w'\f3void \fPgluOrtho2D( 'u
+	GLdouble \fIright\fP,
+	GLdouble \fIbottom\fP,
+	GLdouble \fItop\fP )
+.fi
+
+.EQ
+delim $$
+.EN
+.SH PARAMETERS
+.TP \w'\f2left\fP\ \f2right\fP\ \ 'u 
+\f2left\fP, \f2right\fP
+Specify the coordinates for the left and right vertical clipping planes.
+.TP
+\f2bottom\fP, \f2top\fP
+Specify the coordinates for the bottom and top horizontal clipping planes.
+.SH DESCRIPTION
+\%\f3gluOrtho2D\fP sets up a two-dimensional orthographic viewing region.  
+This is equivalent to calling \f3glOrtho\fP with $ near ~=~ -1 $ and 
+$ far ~=~ 1 $.
+.SH SEE ALSO
+\f3glOrtho(3G)\fP, \%\f3gluPerspective(3G)\fP
+