[Ada] Remove left-overs of front-end SJLJ processing
gcc/ada/
* gcc-interface/gigi.h (enum standard_datatypes): Remove values
for the SJLJ exception mechanism.
(jmpbuf_type): Delete.
(jmpbuf_ptr_type): Likewise.
(get_jmpbuf_decl): Likewise.
(set_jmpbuf_decl): Likewise.
(get_excptr_decl): Likewise.
(not_handled_by_others_decl): Likewise.
(setjmp_decl): Likewise.
(update_setjmp_buf_decl): Likewise.
(raise_nodefer_decl): Likewise.
(set_block_jmpbuf_decl): Likewise.
(get_block_jmpbuf_decl): Likewise.
* gcc-interface/trans.cc (gigi): Delete dead code.
* gcc-interface/utils.cc (gnat_binding_level): Remove JMPBUF_DECL.
(gnat_pushlevel): Do not clear it.
(set_block_jmpbuf_decl): Delete.
(get_block_jmpbuf_decl): Likewise.