Add an option to suppress the persistent result variable when running EvaluateExpression
from Python.  If you don't need to refer to the result in another expression, there's no
need to bloat the persistent variable table with them since you already have the result
SBValue to work with.

<rdar://problem/17963645>
Change __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ for versions > 10.9.

The previous encoding only allowed a single digit for the minor version
number. This changes it to use 2 digits for both the minor version and the
revision number.