Build system improvements: (cross compilation, libnode, etc)

- utilizing autoconf configure.guess to output canonical $target_{cpu,vendor,os}
- normalizing $target_cpu --> $arch according to v8 naming scheme
- normalizing $target_os --> $platform according to v8 naming scheme
- renamed c-ares platform-arch directories to represent v8 canonical names
- new targets in Makefile: libnode-{static,dynamic}[-debug]
- scons is symbolized as SCONS in Makefile for portability/flexibility.
- LINKFLAGS inherith from LDFLAGS ("magic" variable exported by autoconf and configure).
- When building on OS X, CFLAGS and LDFLAGS will contain appropriate -arch flag, set up by configure (instead of the Makefile).
- libv8.a make targets cleaned up with unison libv8_flags set of flags.
- the clean make target now cleans up libraries (libv8, libnode, etc).
- added config.guess, config.sub and install-sh (utilized by autoconf/configure)