fix for bcc version built from source

[gpchelkin]

>>> import bcc
>>> bcc.__version__
'0.26.0-50418003'
>>> tuple(map(int, bcc.__version__.split(".")))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: invalid literal for int() with base 10: '0-50418003'

[elesiuta]

Looks good, thanks!