Linux: Add ppoll fortify symbol for 64 bit time_t (BZ# 29746)

Similar to ppoll, the poll.h header needs to redirect the poll call
to a proper fortified ppoll with 64 bit time_t support.

The implementation is straightforward, just need to add a similar
check as __poll_chk and call the 64 bit time_t ppoll version.  The
debug fortify tests are also extended to cover 64 bit time_t for
affected ABIs.

Unfortunately it requires an aditional symbol, which makes backport
tricky.  One possibility is to add a static inline version if compiler
supports is and call abort instead of __chk_fail, so fortified version
will call __poll64 in the end.

Another possibility is to just remove the fortify support for
_TIME_BITS=64.

Checked on i686-linux-gnu.

sysdeps/unix/sysv/linux/Versions

@@ -313,6 +313,11 @@ libc {
     process_madvise;
     process_mrelease;
   }
+  GLIBC_2.37 {
+%ifdef TIME64_NON_DEFAULT
+    __ppoll64_chk;
+%endif
+  }
   GLIBC_PRIVATE {
     # functions used in other libraries
     __syscall_rt_sigqueueinfo;