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, 5 insertions, 0 deletions

diff --git a/sysdeps/ieee754/ldbl-opt/w_ilogb.c b/sysdeps/ieee754/ldbl-opt/w_ilogb.c
new file mode 100644
index 0000000000..f518087a5f
--- /dev/null
+++ b/sysdeps/ieee754/ldbl-opt/w_ilogb.c
@@ -0,0 +1,5 @@
+#include <math_ldbl_opt.h>
+#include <math/w_ilogb.c>
+#if LONG_DOUBLE_COMPAT(libm, GLIBC_2_0)
+compat_symbol (libm, __ilogb, ilogbl, GLIBC_2_0);
+#endif