gc, gopack: add some missing flags to the docs.

R=rsc, r
CC=golang-dev
https://golang.org/cl/4260051

src/cmd/gc/doc.go

@@ -43,6 +43,8 @@ Flags:
 		disable optimization
 	-S
 		write assembly language text to standard output
+	-u
+		disallow importing packages not marked as safe
 	-V
 		print the compiler version
 

src/cmd/gopack/ar.c

@@ -109,7 +109,7 @@ typedef struct Hashchain
 
 		/* constants and flags */
 char	*man =		"mrxtdpq";
-char	*opt =		"uvnbailoS";
+char	*opt =		"uvnbailogS";
 char	artemp[] =	"/tmp/vXXXXX";
 char	movtemp[] =	"/tmp/v1XXXXX";
 char	tailtemp[] =	"/tmp/v2XXXXX";

src/cmd/gopack/doc.go

@@ -12,10 +12,12 @@ It adds a special Go-specific section __.PKGDEF that collects all the
 Go type information from the files in the archive; that section is
 used by the compiler when importing the package during compilation.
 
-Usage: gopack [uvnbailo][mrxtdpq] archive files ...
+Usage: gopack [uvnbailogS][mrxtdpq] archive files ...
 
 The new option 'g' causes gopack to maintain the __.PKGDEF section
 as files are added to the archive.
 
+The new option 'S' forces gopack to mark the archive as safe.
+
 */
 package documentation