dwarf2cfi: Dump row differences before asserting

dwarf2cfi: Dump row differences before asserting

If maybe_record_trace_start fails because the CFI is inconsistent on two
paths into a block it currently just ICEs.  This changes it to also dump
the CFI on those two paths in the dump file; debugging it without that
information is hopeless.

	* dwarf2cfi.c (dump_cfi_row): Add forward declaration.
	(maybe_record_trace_start): If the CFI is different on the new and
	old paths, print out both to the dump file before ICEing.

From-SVN: r242046