Because one entry point is simpler than two, we make replace_init fulfil
both the roles of replace_init and replace_get_bridge.
Note this should be binary compatible with older replace-malloc
libraries, albeit not detecting their bridge (and with the
previous change, they do not register anyways). So loading older
replace-malloc libraries should do nothing, but not crash in awful ways.
The allocator API is a moving target, and every time we change it, the
surface for replace-malloc libraries grows. This causes some build
system problems, because of the tricks in replace_malloc.mk, which
require the full list of symbols.
Considering the above and the goal of moving some of the replace-malloc
libraries into mozglue, it becomes simpler to reduce the replace-malloc
exposure to the initialization functions.
So instead of the allocator poking into replace-malloc libraries for all
the functions, we expect their replace_init function to alter the table
of allocator functions it's passed to register its own functions.
This means replace-malloc implementations now need to copy the original
table, which is not a bad thing, as it allows function calls with one
level of indirection less. It also replace_init functions to not
actually register the replace-malloc functions in some cases, which will
be useful when linking some replace-malloc libraries into mozglue.
Note this is binary compatible with previously built replace-malloc
libraries, but because those libraries wouldn't update the function
table, they would stay disabled.
