r2649: - used some cpp tricks to make users of talloc() and talloc_realloc()

r2649: - used some cpp tricks to make users of talloc() and talloc_realloc()
  to get auto-naming of pointers very cheaply.

- fixed a couple of memory leaks found with the new tricks

A typical exit report for smbd is now:

talloc report on 'null_context' (total 811 bytes in 54 blocks)
        auth/auth_sam.c:334            contains     20 bytes in   1 blocks
        struct auth_serversupplied_info contains    498 bytes in  33 blocks
        UNNAMED                        contains      8 bytes in   1 blocks
        lib/data_blob.c:40             contains     16 bytes in   1 blocks
        iconv(CP850,UTF8)              contains     61 bytes in   4 blocks
        iconv(UTF8,CP850)              contains     61 bytes in   4 blocks
        iconv(UTF8,UTF-16LE)           contains     67 bytes in   4 blocks
        iconv(UTF-16LE,UTF8)           contains     67 bytes in   4 blocks
        UNNAMED                        contains     13 bytes in   1 blocks

which is much better than before
(This used to be commit 6e721393d03afd3c2f8ced8422533547a9e33342)