Automatically model dynamic symbols

[offlinemark]

If we are analyzing a dynamically linked binary, and we have models implemented for dynamic symbols it requires, we should automatically apply those models.

[yan]

This might bump symbol resolution in priority, since we'd need to do it anyway. This will also let us do things like:

@m.hook('strcpy')
def strcpy(state):
    state.invoke_model(models.strcpy)

[ehennenfent]

https://github.com/trailofbits/manticore/wiki/Ideas