Properly mark all internal function definitions.

Properly mark all internal function definitions.

Since we banned old style function definitions GCC is able to diagnose
function definitions that don't match the function declaration:

  elf32_getehdr.c:78: error: conflicting types for ‘__elf64_getehdr_wrlock’
  libelfP.h:498: note: previous declaration of ‘__elf64_getehdr_wrlock’

This happens on i386 because there internal functions are marked with:

  # define internal_function __attribute__ ((regparm (3), stdcall))

Make sure all internal function declarations and definitions are marked
with internal_function.

Signed-off-by: Mark Wielaard <mjw@redhat.com>