Support building a top-level src/sconsbuild directory. * Change the name of $DESTINATION_ROOT (the Debug or Release directory)   to $TOP_BUILDDIR, name borrowed from autoconf for familiarity * Change the name of $MAIN_DIR to $SCONSBUILD_DIR, just so it's a   little more obvious. * Allow $SCONSBUILD_DIR to be set from the 'scons_settings'   block of a .gyp file's data.  Default value is '#' (top of   the SCons tree) if it's not set in the .gyp. * Pass the .gyp data dict to GenerateSConscriptWrapper so it   can look for scons_settings. Review URL: http://codereview.chromium.org/53132
Support building a top-level src/sconsbuild directory.
* Change the name of $DESTINATION_ROOT (the Debug or Release directory)
  to $TOP_BUILDDIR, name borrowed from autoconf for familiarity
* Change the name of $MAIN_DIR to $SCONSBUILD_DIR, just so it's a
  little more obvious.
* Allow $SCONSBUILD_DIR to be set from the 'scons_settings'
  block of a .gyp file's data.  Default value is '#' (top of
  the SCons tree) if it's not set in the .gyp.
* Pass the .gyp data dict to GenerateSConscriptWrapper so it
  can look for scons_settings.
Review URL: http://codereview.chromium.org/53132
old8xp/gyp_from_google,old8xp/gyp_from_google,old8xp/gyp_from_google,old8xp/gyp_from_google,old8xp/gyp_from_google