Fix ilogb exception and errno (bug 6794)

[BZ #6794]
Following Joseph comments about bug 6794, here is a proposed fix. It turned out
to be a large fix mainly because I had to move some file along to follow libm
files/names conventions.

Basically I have added wrappers (w_ilogb.c, w_ilogbf.c, w_ilogbl.c) that now calls
the symbol '__ieee754_ilogb'. The wrappers checks for '__ieee754_ilogb' output and
set the errno and raise exceptions as expected.

The '__ieee754_ilogb' is implemented in sysdeps. I have moved the 's_ilogb[f|l]' files
to e_ilogb[f|l] and renamed the '__ilogb[f|l]' to '__ieee754_ilogb[f|l]'.

I also found out a bug in i386 and x86-64 assembly coded ilogb implementation where
it raises a FE_DIVBYZERO when argument is '0.0'. I corrected this issue as well.

Finally I added the errno and FE_INVALID tests for 0.0, NaN and +-InF argument. Tested
on i386, x86-64, ppc32 and ppc64.

1 files changed, 1 insertions, 2 deletions

diff --git a/sysdeps/ieee754/ldbl-128ibm/s_ilogbl.c b/sysdeps/ieee754/ldbl-128ibm/e_ilogbl.c
index a6f0e1e678..55f87ed422 100644
--- a/sysdeps/ieee754/ldbl-128ibm/s_ilogbl.c
+++ b/sysdeps/ieee754/ldbl-128ibm/e_ilogbl.c
@@ -29,7 +29,7 @@ static char rcsid[] = "$NetBSD: $";
 #include <math_private.h>
 #include <math_ldbl_opt.h>
 
-int __ilogbl(long double x)
+int __ieee754_ilogbl(long double x)
 {
 	int64_t hx,lx;
 	int ix;
@@ -55,4 +55,3 @@ int __ilogbl(long double x)
 	}
 	return FP_ILOGBNAN;
 }
-long_double_symbol (libm, __ilogbl, ilogbl);