Tidy up m_oset.c
- Document that the allocation function must ot return NULL.
- As a conequence of the previous requirement the various Create and AllocNode
  functions cannot return NULL. Remove pointless asserts at call sites.
- Remove documentation of undefined function  CreateWithCmp.
- Names of library functions (such as 'free') are reserved as a are names
  beginning with underscores. Don't use those.


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@14531 a5019735-40e9-0310-863c-91ae7b9d1cf9
Document the NULL-ness of the return values of HT_construct and HT_to_array.
Audit call sites.


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@14532 a5019735-40e9-0310-863c-91ae7b9d1cf9
Document that VG_(newSWA) never returns NULL (because its
allocation function does not). Audit call sites.


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@14533 a5019735-40e9-0310-863c-91ae7b9d1cf9