emulate lazy relocation as deferrable relocation

traditional lazy relocation with call-time plt resolver is
intentionally not implemented, as it is a huge bug surface and demands
significant amounts of arch-specific code and requires ongoing
maintenance to ensure compatibility with applications which make use
of new additions to the arch's register file in passing function
arguments.

some applications, however, depend on the ability to dlopen modules
which have unsatisfied symbol references at the time they are loaded,
either avoiding use of the affected interfaces or manually loading
another module to provide the missing definition via their own module
dependency tracking outside the ELF data structures. while such usage
is non-conforming, failure to support it has been a significant
obstacle for users/distributions trying to support affected software,
particularly the X.org server.

instead of resolving lazy relocations at call time, this patch saves
unresolved GOT/PLT relocations for deferral and retries them after
each subsequent dlopen until they are resolved. since dlopen is the
only time at which the effective global symbol table can change, this
behavior is not observably different from traditional lazy binding,
and the required code is minimal.

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