Hardware convenience library

The only target dependency for most hardware is sizeof(target_phys_addr_t).
Build these files into a convenience library, and use that instead of
building for every target.

Remove and poison various target specific macros to avoid bogus target
dependencies creeping back in.

Big/Little endian is not handled because devices should not know or care
about this to start with.

Signed-off-by: Paul Brook <paul@codesourcery.com>

.gitignore

@@ -4,6 +4,8 @@ i386
 *-darwin-user
 *-linux-user
 *-bsd-user
+libhw32
+libhw64
 qemu-doc.html
 qemu-tech.html
 qemu-doc.info