Add truncl tests related to BZ#16414

Backport of 4655c291d1808c35b7c54236ae62be7a3aaa0a2d
PowerPC: remove wrong ceill implementation for PowerPC64

The ceill assembly implementation (sysdeps/powerpc/powerpc64/fpu/s_ceill.S)
returns wrong results for some inputs where first double is a exact
integer and the precision is determined by second long double.

Checking on implementation comments and history, I am very confident the
assembly implementation was based on a version before commit
5c68d401698a58cf7da150d9cce769fa6679ba5f that fixes BZ#2423 (Errors in
long double (ldbl-128ibm) rounding functions in glibc-2.4).

By just removing the implementation and make the build select
sysdeps/ieee754/ldbl-128ibm/s_ceill.c instead fixes the failing math.

Fixes BZ#16701.

Backport of 374f7f61214967bb4e2257695aeeeecc2a77f369
PowerPC: remove wrong nearbyintl implementation for PPC64

The nearbyintl assembly implementation
(sysdeps/powerpc/powerpc64/fpu/s_nearbyintl.S)
returns wrong results for some inputs where first double is a exact
integer and the precision is determined by second long double.

Checking on implementation comments and history, I am very confident the
assembly implementation was based on a version before commit
5c68d401698a58cf7da150d9cce769fa6679ba5f that fixes BZ#2423 (Errors in
long double (ldbl-128ibm) rounding functions in glibc-2.4).

By just removing the implementation and make the build select
sysdeps/ieee754/ldbl-128ibm/s_nearbyintl.c instead fixes the failing
math.

Fixes BZ#16706.

Backport of 98fb27a373f37554232e0060eef1a5bb00a07eb0
PowerPC: remove wrong roundl implementation for PowerPC64

The roundl assembly implementation
(sysdeps/powerpc/powerpc64/fpu/s_roundl.S)
returns wrong results for some inputs where first double is a exact
integer and the precision is determined by second long double.

Checking on implementation comments and history, I am very confident the
assembly implementation was based on a version before commit
5c68d401698a58cf7da150d9cce769fa6679ba5f that fixes BZ#2423 (Errors in
long double (ldbl-128ibm) rounding functions in glibc-2.4).

By just removing the implementation and make the build select
sysdeps/ieee754/ldbl-128ibm/s_roundl.c instead fixes the failing math.

This fixes 16707.

Backport of c7de50250367167d8c9f35594b264f6a0af8dd0c