Vector extensions not handled correctly for >>=,

I noticed a small issue with icc's support for GCC vector extensions: the >>= and <<= operators seem to be broken.

Here is a quick example (or, on Compiler Explorer if you prefer):

#include <stdint.h>

typedef int32_t vec __attribute__((__vector_size__(16)));

vec se(vec a) {
#if defined(CONFUSE_ICC)
  a >>= 31;
#else
  a = a >> 31;
#endif

  return a;
}

If you define CONFUSE_ICC, that will result in something like

foo.c(7): error: expression must have integral or unscoped enum type
    a >>= 31;
    ^

compilation aborted for foo.c (code 2)
Compiler returned: 2

As you can see, the workaround is straightforward enough, I just thought I should report the bug.