treewide: be explicit about dependence on trace.h & trace2.h

Dozens of files made use of trace and trace2 functions, without
explicitly including trace.h or trace2.h.  This made it more difficult
to find which files could remove a dependence on cache.h.  Make C files
explicitly include trace.h or trace2.h if they are using them.

Signed-off-by: Elijah Newren <newren@gmail.com>
Acked-by: Calvin Wan <calvinwan@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

compat/simple-ipc/ipc-unix-socket.c

@@ -4,6 +4,7 @@
 #include "strbuf.h"
 #include "pkt-line.h"
 #include "thread-utils.h"
+#include "trace2.h"
 #include "unix-socket.h"
 #include "unix-stream-server.h"