More symmetric between push_all() and pull_all()
More symmetric between push_all() and pull_all()

push_all() does not work correctly if (len > INT_MAX), so int is more simple.
push_all() should not return -2. It propagates to mg_write(), but mg_write() must not return -2.

GerHobbelt/civet-webserver,GerHobbelt/civet-webserver,GerHobbelt/civet-webserver,GerHobbelt/civet-webserver,GerHobbelt/civet-webserver,GerHobbelt/civet-webserver