Call jl_sigatomic_begin at the end of init_julia block

This is required for using `reenable_sigint` in `pyjlwrap_call`.

See: PyCall 574

Author: tkf

julia/core.py

@@ -635,6 +635,8 @@ def __init__(self, init_julia=True, jl_init_path=None, runtime=None,
                 end
                 """)
 
+            self.api.jl_sigatomic_begin()
+
         # Whether we initialized Julia or not, we MUST create at least one
         # instance of PyObject and the convert function. Since these will be
         # needed on every call, we hold them in the Julia object itself so