MFC: r328834
o Let rtld(1) set up psABI user trap handlers prior to executing the
objects' init functions instead of doing the setup via a constructor in libc as the init functions may already depend on these handlers to be in place. This gets us rid of: - the undefined order in which libc constructors as __guard_setup() and jemalloc_constructor() are executed WRT __sparc_utrap_setup(), - the requirement to link libc last so __sparc_utrap_setup() gets called prior to constructors in other libraries (see r122883). For static binaries, crt1.o still sets up the user trap handlers.
o Move misplaced prototypes for MD functions in to the MD prototype
section of rtld.h.
o Sprinkle nitems().