Clean up the usage of V8_TARGET_ARCH_${arch} and V8_HOST_ARCH_${arch}

Clean up the usage of V8_TARGET_ARCH_${arch} and V8_HOST_ARCH_${arch}

R=jkummerow@chromium.org

Committed: http://code.google.com/p/v8/source/detail?r=15391

[haitao.feng, 2013-06-27 08:56:30]

It seems that we could use #if directly when using the V8_TARGET_ARCH_${arch}
and V8_HOST_ARCH_${arch}. As once those macro is defined, they are always
defined to be 1.
  1) Defined from gyp: -DV8_TARGET_ARCH_${arch}, it is 1 from gcc manual
(http://gcc.gnu.org/onlinedocs/gcc/Preprocessor-Options.html#Preprocessor-Options):
  2) From globals.h: It is 1 if detected.

[haitao.feng, 2013-06-28 01:43:46]

Add Paul Lind for the MIPS port.

[Jakob Kummerow, 2013-06-28 10:58:00]

LGTM, I'll land.

[Jakob Kummerow, 2013-06-28 15:35:29]

Committed patchset #1 manually as r15391 (presubmit successful).