misc: Only use custom lround() under DISABLE_SOME_FLOATING_POINT

On my Core2, the library version of lround() is faster than our
hand-rolled non-floating point implementation. So only enable our code
if we are trying to minimise the number of floating point operations --
even then, it would worth investigating the library performance first.

[Just a reminder that optimisation choices will change over time as our
hardware and software evolves.]

src/cairo-misc.c

@@ -463,6 +463,7 @@ _cairo_operator_bounded_by_either (cairo_operator_t op)
 
 }
 
+#if DISABLE_SOME_FLOATING_POINT
 /* This function is identical to the C99 function lround(), except that it
  * performs arithmetic rounding (floor(d + .5) instead of away-from-zero rounding) and
  * has a valid input range of (INT_MIN, INT_MAX] instead of
@@ -673,6 +674,7 @@ _cairo_lround (double d)
 #undef MSW
 #undef LSW
 }
+#endif
 
 /* Convert a 32-bit IEEE single precision floating point number to a
  * 'half' representation (s10.5)

src/cairo-ps-surface.c

@@ -880,8 +880,8 @@ _cairo_ps_surface_get_page_media (cairo_ps_surface_t     *surface)
 	page->name = strdup (page_name);
     } else {
 	snprintf (buf, sizeof (buf), "%dx%dmm",
-		  _cairo_lround (surface->width * 25.4/72),
-		  _cairo_lround (surface->height * 25.4/72));
+		  (int) _cairo_lround (surface->width * 25.4/72),
+		  (int) _cairo_lround (surface->height * 25.4/72));
 	page->name = strdup (buf);
     }
 

src/cairoint.h

@@ -947,8 +947,13 @@ _cairo_round (double r)
     return floor (r + .5);
 }
 
+#if DISABLE_SOME_FLOATING_POINT
 cairo_private int
 _cairo_lround (double d) cairo_const;
+#else
+#define _cairo_lround lround
+#endif
+
 cairo_private uint16_t
 _cairo_half_from_float (float f) cairo_const;