+2011-02-16 Paul Eggert <eggert@cs.ucla.edu>
+
+ longlong: tune, particularly for common case of c99
+
+ * m4/longlong.m4 (AC_TYPE_LONG_LONG_INT): Don't bother compiling
+ or running anything if c99, or if unsigned long long int does not
+ work. In either case, we know the answer without further tests.
+ Do not compile _AC_TYPE_LONG_LONG_SNIPPET twice. Instead, compile
+ it at most once, and use its results for both long long int and
+ unsigned long long int. This is more likely to be efficient in
+ the common case where the program wants to check for both long
+ long int and unsigned long long int.
+ (AC_TYPE_UNSIGNED_LONG_LONG_INT): Don't bother compiling if c99,
+ since the answer is already known.
+