Don't bother with __builtin_floorl().

At least as I read the GCC documentation, if GCC supports a builtin
floorl() at all, it will always treat floorl() and
__builtin_floorl() the same (it's reserved in C90 and defined in C99, so
nobody should ever write C code assuming floorl() won't be treated in
that afshion).

In addition, the GCC 3.3.6 manual says nothing about __builtin_floorl(),
so it probably won't help to use it.  If it appears to help, there's
probably something else going on.

Also, GCC appears not to like "#ifdef (__GNUC__)", as the parentheses
mean it's testing an expression, not a macro name.

Change-Id: Ib88b52c366d7f3b1637bb408fb18d04b67c27e4b
Reviewed-on: https://code.wireshark.org/review/5909
Reviewed-by: Guy Harris <guy@alum.mit.edu>

wsutil/floorl.c

@@ -31,19 +31,8 @@
 long double
 floorl(long double x)
 {
-#ifdef (__GNUC__)
-  /*
-   * Handle platforms where GCC has the builtin but the platform's
-   * headers (including the headers used with GCC!) don't define
-   * floorl() to use it.
-   *
-   * XXX - are there any such platforms?
-   */
-  __builtin_floorl(x);
-#else
   /* Not perfect, but probably the best workaround available */
   return floor((double)x);
-#endif
 }
 
 #endif /* !HAVE_FLOORL */