Fixes #3: various malloc calls on svn_opt_revision_t struct pointers were incorrectly calling sizeof(*ptr), and getting the wrong amount of memory back. Really not sure how this worked before, not sure how big svn_opt_revision_t is supposed to be, maybe 4 bytes just happened to be big enough. This patch fixes all calls of that type to be sizeof(svn_opt_revision_t) instead, which will provide sufficient memory in all cases.