Support bool defaults in utils.update_argspec
Support bool defaults in utils.update_argspec

Previously, boolean default values of arguments passed to
`utils.update_argspec` were treated like int values (since for some
reason True isinstance int), so something like

::

    @update_argspec(('b', True))
    @other_decorator
    def fun(b=True):
        pass

would become

::

    def fun(b=1):
        pass

This commit adds an explicit check for boolean values so they're
treated accordingly.

This patch was taken from the Arakoon repository (which contains a copy of
pyrakoon.utils.update_argspec), changeset 3c1bdd19bbfe.

See: https://bitbucket.org/despiegk/arakoon/changeset/3c1bdd19bbfe/raw/

Incubaid/pyrakoon,Incubaid/pyrakoon