trace: [tcg] Define TCG tracing helper routine wrappers

trace: [tcg] Define TCG tracing helper routine wrappers

Generates header "trace/generated-helpers-wrappers.h" with definitions for TCG
helper wrappers.

These wrappers ('gen_helper_trace_${event}_exec_wrapper') transform mixed native
and TCG argument types to TCG types and call the actual TCG helpers
('gen_helper_trace_${event}_exec_proxy').

Signed-off-by: Lluís Vilanova <vilanova@ac.upc.edu>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>