re PR sanitizer/78307 (missing symbols in libubsan without changing the soname)

	PR sanitizer/78307
	* ubsan/ubsan_handlers.cc (__ubsan_handle_cfi_bad_icall): New function.
	( __ubsan_handle_cfi_bad_icall_abort): Likewise. 
	* ubsan/ubsan_handlers.h (struct CFIBadIcallData): New type.
	* ubsan/ubsan_handlers_cxx.cc (__ubsan_handle_cfi_bad_type): New
	function.
	(__ubsan_handle_cfi_bad_type_abort): Likewise.
	* ubsan/ubsan_handlers_cxx.h (struct CFIBadTypeData): New type.
	(__ubsan_handle_cfi_bad_type): Export function.
	(__ubsan_handle_cfi_bad_type_abort): Likewise.
	* HOWTO_MERGE: Update documentation.

From-SVN: r242478