re PR c++/70035 (Calling a non-virtual member in base-class constructor call with ubsan causes segfault when superclass has virtual member with same name)

	PR c++/70035
	* cp-tree.h (cp_ubsan_maybe_initialize_vtbl_ptrs): New prototype.
	* decl.c (start_preparsed_function): Call
	cp_ubsan_maybe_initialize_vtbl_ptrs if needed.
	* cp-ubsan.c (cp_ubsan_dfs_initialize_vtbl_ptrs,
	cp_ubsan_maybe_initialize_vtbl_ptrs): New functions.

	* g++.dg/ubsan/pr70035.C: New test.

From-SVN: r233984