runtime validation of DT_SYMTAB lookups - why is there no DT_SYMSZ?

[Jacob Burkholder]

I've always used the fact that the symbol table and string table are
present in the binary in that order and adjacent to each other to find
the number of symbol table entries., ie (strtab - (char *)symtab) /
sizeof(*symtab), although clearly this is not required and may just be
gnu ld convention.  DT_SYMSZ would be a useful addition to the ELF
standard IMO.