Fix an invalid memory write tracked down with valgrind.
Fix an invalid memory write tracked down with valgrind.

* subversion/libsvn_client/merge.c
  (do_file_merge): Alloc memory sufficient for a struct not a pointer.

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion