test standalone example only if MSSM is configured
Remove automatic (incomplete) support for input scale in EXTPAR entry 0

SLHA defines EXTPAR entry 0 as:

 1) If the value is 0, the input scale is derived from the condition
    g1 == g2 .

 2) If the value is -1, the input scale is defined as
    sqrt(m_stop1 * m_stop2)

 3) Otherwise, the given fixed value for the input scale will be used.

1) and 2) are in general model-dependent settings.  In FlexibleSUSY
the preferred way to support these three scale choices is to
explicitly set the HighScale variable to one of the following:

 1) HighScale = g1 == g2

 2) HighScale = Sqrt[M[St[1]] * M[St[2]]]

 3) EXTPAR = { {0, Qin}, ... };
    HighScale = Qin