Only use lround in C99 programs.

diff --git a/gfx/cairo/cairo/src/cairo-misc.c b/gfx/cairo/cairo/src/cairo-misc.c
--- a/gfx/cairo/cairo/src/cairo-misc.c
+++ b/gfx/cairo/cairo/src/cairo-misc.c
@@ -478,17 +478,17 @@ _cairo_operator_bounded_by_either (cairo
     case CAIRO_OPERATOR_IN:
     case CAIRO_OPERATOR_DEST_IN:
     case CAIRO_OPERATOR_DEST_ATOP:
 	return 0;
     }
 
 }
 
-#if DISABLE_SOME_FLOATING_POINT
+#if DISABLE_SOME_FLOATING_POINT || __STDC_VERSION__ < 199901L
 /* 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
  * [INT_MIN, INT_MAX]. It is much faster on both x86 and FPU-less systems
  * than other commonly used methods for rounding (lround, round, rint, lrint
  * or float (d + 0.5)).
  *
  * The reason why this function is much faster on x86 than other
diff --git a/gfx/cairo/cairo/src/cairoint.h b/gfx/cairo/cairo/src/cairoint.h
--- a/gfx/cairo/cairo/src/cairoint.h
+++ b/gfx/cairo/cairo/src/cairoint.h
@@ -969,17 +969,17 @@ _cairo_restrict_value (double value, dou
  * away from 0. _cairo_round rounds halfway cases toward negative infinity.
  * This matches the rounding behaviour of _cairo_lround. */
 static inline double cairo_const
 _cairo_round (double r)
 {
     return floor (r + .5);
 }
 
-#if DISABLE_SOME_FLOATING_POINT
+#if DISABLE_SOME_FLOATING_POINT || __STDC_VERSION__ < 199901L
 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;