javascript: Fix build for nodejs v5 which has smaller version string

javascript: Fix build for nodejs v5 which has smaller version string

SWIG uses SWIG_V8_VERSION made of
0x0${V8_VERSION_MAJOR}${V8_VERSION_MINOR}${V8_VERSION_PATCH}. Because newer v8
versions don't seem to have a patch version that is padded the version string
ends up too small ending with using the node.js 0.10.x paths. This fix pads the
version string to 8chars which (we assume) is always correct. Fixes #358

Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>