Fix PR65261

Fix PR65261

Running bootstrap-ubsan on ppc64le shows many instances of:

  libcpp/lex.c:552:30: runtime error: load of misaligned address
  0x01001f31d37a for type 'const uchar', which requires 16 byte alignment

But the unaligned vector loads are intended in this case, because they
are preferable to forced-alignment on POWER8. So just silence the ubsan
errors.

2015-03-02  Markus Trippelsdorf  <markus@trippelsdorf.de>

include/
	PR target/65261
	* ansidecl.h (ATTRIBUTE_NO_SANITIZE_UNDEFINED): New macro.

libcpp/
	PR target/65261
	* lex.c (search_line_fast): Silence ubsan errors.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@221190 138bc75d-0d04-0410-961f-82ee72b054a4