Fix compilation warnings in --with-wide-int build on Windows

Fix compilation warnings in --with-wide-int build on Windows

* src/comp.c (emit_rvalue_from_emacs_uint)
(emit_rvalue_from_lisp_word_tag): Fix comparison of unsigned
values.
(gcc_jit_context_new_rvalue_from_ptr): Define only if
LISP_WORDS_ARE_POINTERS, to avoid compilation warning.
(init_gccjit_functions): Load gcc_jit_context_new_rvalue_from_ptr
only if LISP_WORDS_ARE_POINTERS.