The preprocessor defines check for v5t and v5te.  This patch adds v7 and
v7-a which provide support for -march=armv7 and -mcpu=cortex-a8
respectively.
This is to support my work compiling chromium on arm, see
http://crbug.com/12028
http://codereview.chromium.org/115509


git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@2001 ce2b1a6d-e550-0410-aec6-3dcde31c8c00