SWIG: update library to 2.0.10

this is latest version, changelog can be seen here:
http://www.swig.org/release.html
SWIG: make MacOS and Linux share the swig dir

put it in external/common/
SWIG: update swiglib path

to external/common/share/swig
swig: update the Linux swig executable, !Mac needs update too

downloaded and built swig (2.0.10) on local machine and distribute the executable
swig file. Please build one for Mac and add it too!
remove libstdc++ license

we no longer link statically to libstdc++
see https://github.com/numenta/nupic/wiki/Configuration-and-Build-System
and NPC-59
swig: workaround namespace for swig>2.0.3 and gcc <4.8