ARM: Workaround for a NEON bug in assembler from binutils 2.18

ARM: Workaround for a NEON bug in assembler from binutils 2.18

The problem was reported as bug 25534 against pixman in
freedesktop.org bugzila. Link to a patch for binutils:
http://sourceware.org/ml/binutils/2008-03/msg00260.html

For pixman the impact is a build failure when using
binutils 2.18. Versions 2.19 and higer are fine. Still
some distros may be using older versions of binutils and
this is causing problems.

This patch workarounds the problem by replacing a problematic
"vmov a, b" instruction with equivalent "vorr a, b, b". Actually
they even map to the same instruction opcode in the generated
code, so the resulting binary is identical with and without patch.