linker_glue.c: correct handling of allocation site in __wrap_calloc.
linker_glue.c: make underlying_ symbols non-static and ident-protected.
Support static linking wrap hooks. Refactor linker glue.

--HG--
rename : linker_glue.c => common_linker_glue.c
rename : linker_glue.c => dynamic_linker_glue.c
rename : linker_glue.c => static_linker_glue.c
Minor fix to avoid malloc_usable_size getting implicit declaration.
Cleanup the mess of glue and inc.c files. Now the only include is generic.inc.c, and glue goes mostly in the top-level hooks files.

--HG--
rename : hook_protos.inc.c => hook_protos.h
rename : malloc_hooks.c => malloc_hooks_glibc.c
Major overhaul to simplify hooks, enable real composability and separate core malloc hook path from 'high-level' pre/post hooks.

--HG--
rename : hook_protos.h => alloc_events.h
rename : generic.inc.c => event_hooks.c
rename : malloc_hooks_glibc.c => malloc_hook_stubs_glibc.c
rename : dynamic_linker_glue.c => malloc_hook_stubs_preload.c