PowerPC malloc alignment

[Daniel Jacobowitz]

The malloc alignment on PowerPC (32-bit) was bumped up to 16 bytes
just before glibc 2.4 and then immediately reverted.  I eventually
found the discussion of the reversion here:

  https://bugzilla.redhat.com/show_bug.cgi?id=183895

Jakub, were there more lurking problems than just the one you fixed in
the patch attached to that bug?

The current status breaks, among other things, GDB when built with
"-maltivec -mabi=altivec -mlong-double-128".  A 16-byte union
including a long double is allocated in the heap and copied using
lvx / stvx, which require a 16-byte aligned address.

-- 
Daniel Jacobowitz
CodeSourcery