missing logbl(3) where 64-bit long double

[George Koehler]

Hello tech list,

OpenBSD's libm is missing logbl(3) function on archs where long double
is double.  The missing logbl breaks my builds of "NEW: devel/dtools"
(ports list) on macppc and powerpc64.  I guess that other software
avoids logbl and prefers ilogbl(3) or frexp(3).

This diff adds logbl and fixes dtools, ok?
--George

Index: src/s_logb.c
===================================================================
RCS file: /cvs/src/lib/libm/src/s_logb.c,v
retrieving revision 1.4
diff -u -p -r1.4 s_logb.c
--- src/s_logb.c        12 Sep 2016 19:47:02 -0000      1.4
+++ src/s_logb.c        14 Oct 2021 21:49:22 -0000
@@ -33,3 +33,4 @@ logb(double x)
                return (double) (ix-1023); 
 }
 DEF_STD(logb);
+LDBL_MAYBE_UNUSED_CLONE(logb);