libc: Remove support for pre-C99 C standards

Reviewed by:	jhb
Differential Revision:	https://reviews.freebsd.org/D43254

lib/libc/stdlib/div.c

@@ -41,34 +41,6 @@ div(int num, int denom)
 
 	r.quot = num / denom;
 	r.rem = num % denom;
-#if !defined(__STDC_VERSION__) || (__STDC_VERSION__ < 199901L)
+
-	/*
-	 * The ANSI standard says that |r.quot| <= |n/d|, where
-	 * n/d is to be computed in infinite precision.  In other
-	 * words, we should always truncate the quotient towards
-	 * 0, never -infinity.
-	 *
-	 * Machine division and remainer may work either way when
-	 * one or both of n or d is negative.  If only one is
-	 * negative and r.quot has been truncated towards -inf,
-	 * r.rem will have the same sign as denom and the opposite
-	 * sign of num; if both are negative and r.quot has been
-	 * truncated towards -inf, r.rem will be positive (will
-	 * have the opposite sign of num).  These are considered
-	 * `wrong'.
-	 *
-	 * If both are num and denom are positive, r will always
-	 * be positive.
-	 *
-	 * This all boils down to:
-	 *	if num >= 0, but r.rem < 0, we got the wrong answer.
-	 * In that case, to get the right answer, add 1 to r.quot and
-	 * subtract denom from r.rem.
-	 */
-	if (num >= 0 && r.rem < 0) {
-		r.quot++;
-		r.rem -= denom;
-	}
-#endif
 	return (r);
 }

lib/libc/stdlib/imaxdiv.c

@@ -36,11 +36,6 @@ imaxdiv(intmax_t numer, intmax_t denom)
 
 	retval.quot = numer / denom;
 	retval.rem = numer % denom;
-#if !defined(__STDC_VERSION__) || (__STDC_VERSION__ < 199901L)
+
-	if (numer >= 0 && retval.rem < 0) {
-		retval.quot++;
-		retval.rem -= denom;
-	}
-#endif
 	return (retval);
 }

lib/libc/stdlib/ldiv.c

@@ -43,11 +43,6 @@ ldiv(long num, long denom)
 
 	r.quot = num / denom;
 	r.rem = num % denom;
-#if !defined(__STDC_VERSION__) || (__STDC_VERSION__ < 199901L)
+
-	if (num >= 0 && r.rem < 0) {
-		r.quot++;
-		r.rem -= denom;
-	}
-#endif
 	return (r);
 }

lib/libc/stdlib/lldiv.c

@@ -36,11 +36,6 @@ lldiv(long long numer, long long denom)
 
 	retval.quot = numer / denom;
 	retval.rem = numer % denom;
-#if !defined(__STDC_VERSION__) || (__STDC_VERSION__ < 199901L)
+
-	if (numer >= 0 && retval.rem < 0) {
-		retval.quot++;
-		retval.rem -= denom;
-	}
-#endif
 	return (retval);
 }