acme: import event log from plan9port (thanks fshahriar)

Based off the following 3 commits:

	4a3fb87264f8bc03fc62f00ef335056f30d18023
	45f8ba54143323f08a21343633764caa59aa3ea3
	fdf6ef333705c844bcf3ccf2f93b2773f1a6aa41

Reading /mnt/acme/log reports a log of window create,
put, focus, and delete events, as they happen. It blocks
until the next event is available.

Example log output:

	8 new /Users/rsc/foo.go
	8 put /Users/rsc/foo.go
	8 del /Users/rsc/foo.go

This lets acme-aware programs react to file writes, for example
compiling code, running a test, or updating an import block.

1 files changed, 13 insertions, 1 deletions

diff --git a/sys/src/cmd/acme/xfid.c b/sys/src/cmd/acme/xfid.c
index 2feb438b2..db4c55731 100644
--- a/sys/src/cmd/acme/xfid.c
+++ b/sys/src/cmd/acme/xfid.c
@@ -63,6 +63,8 @@ xfidflush(Xfid *x)
 	Column *c;
 	Xfid *wx;
 
+	xfidlogflush(x);
+
 	/* search windows for matching tag */
 	qlock(&row);
 	for(j=0; j<row.ncol; j++){
@@ -98,9 +100,9 @@ xfidopen(Xfid *x)
 
 	w = x->f->w;
 	t = &w->body;
+	q = FILE(x->f->qid);
 	if(w){
 		winlock(w, 'E');
-		q = FILE(x->f->qid);
 		switch(q){
 		case QWaddr:
 			if(w->nopen[q]++ == 0){
@@ -179,6 +181,13 @@ xfidopen(Xfid *x)
 		}
 		winunlock(w);
 	}
+	else{
+		switch(q){
+		case Qlog:
+			xfidlogopen(x);
+			break;
+		}
+	}
 	fc.qid = x->f->qid;
 	fc.iounit = messagesize-IOHDRSZ;
 	x->f->open = TRUE;
@@ -274,6 +283,9 @@ xfidread(Xfid *x)
 		case Qindex:
 			xfidindexread(x);
 			return;
+		case Qlog:
+			xfidlogread(x);
+			return;
 		default:
 			warning(nil, "unknown qid %d\n", q);
 			break;