smartptr: Remove assertions, change intptr_t to unsigned int

ePtr is used a lot, so assertions are expensive (they'll create a
branch in the code). Since no good ever came of these anyway, just
remove them from the class.

Change intptr_t to just integer, hoping to avoid the SWIG message:
"python detected a memory leak of type 'intptr_t *', no destructor found"
Merge remote-tracking branch 'pli/master'

# By Mike Looijmans
# Via Mike Looijmans
* pli/master:
  smartptr: Remove assertions, change intptr_t to unsigned int