Fix stack alignment corruption for MinGW32 build

Contributed by Peter Varga <pvarga@inf.u-szeged.hu>

BUG=
TEST=cctest/test-assembler-ia32/StackAlignmentForSSE2,cctest/test-assembler-x64/StackAlignmentForSSE2,cctest/test-platform/StackAlignment
R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/18300003

Patch from Peter Varga <pvarga@inf.u-szeged.hu>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15502 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Tweak error message

R=yangguo@chromium.org
BUG=v8:2758

Review URL: https://codereview.chromium.org/18759002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15503 ce2b1a6d-e550-0410-aec6-3dcde31c8c00