Port to Oracle Developer Studio 12.6

Port to Oracle Developer Studio 12.6

This compiler is a bit pickier about checking conformance to
the C standard, ranging from syntax trivia (no extra ";" at
the top level) to portability trivia (warnings re conversion
between function and data pointers) to more-important stuff
like lack of support for some __attribute__ usages.
* src/dynlib.c (dynlib_addr): First argument is a function
pointer, not a data pointer.  All callers changed.
* src/emacs-module.c (module_function_address):
Return module_funcptr, not void *.  All uses changed.
* src/lisp.h (module_funcptr) [HAVE_MODULES]: New type.
* src/lread.c (union ieee754_double): Don’t assume the usual
semantics for converting signed to unsigned int when initializing
a bitfield, as the Oracle compiler complains and the C standard
is unclear.
* src/pdumper.c (ALLOW_IMPLICIT_CONVERSION): Make it clearer
that -Wsign-conversion is disabled everywhere in this file.
(dump_trace, dump_tailq_prepend, dump_tailq_append):
Don’t assume __attribute__.
(dump_object_self_representing_p): Don’t disable conversion
warnings; it’s not needed here.
(DEFINE_FROMLISP_FUNC): Avoid possible signal in integer
conversion from unsigned to signed.
(DEFINE_FROMLISP_FUNC, finish_dump_pvec): Avoid warning about
unreachable statements on platforms not supporting the
__attribute__.
(intmax_t_from_lisp, intmax_t_to_lisp, dump_off_from_lisp)
(dump_off_to_lisp, dump_emacs_reloc_immediate_lv)
(dump_emacs_reloc_immediate_ptrdiff_t)
(dump_emacs_reloc_immediate_intmax_t)
(dump_emacs_reloc_immediate_int, dump_emacs_reloc_immediate_bool):
Omit stray semicolon that violates C standard.
(dump_metadata_for_pdumper): Add cast to pacify compiler complaining
about conversion from function pointer to data pointer.
(Fdump_emacs_portable): Do not use CALLN to call a function
with zero arguments, as C99 prohibits empty initializers.
* src/xdisp.c (syms_of_xdisp): Do not nest calls to pure_list,
to work around a bug in Oracle Developer Studio 12.6.