add top-level package comments for net, reflect, malloc.

reflect is a little more detailed than some because it affords an opportunity
to explain how to approach the library.

R=gri, rsc
CC=go-dev
http://go/go-review/1026026

1 files changed, 3 insertions, 0 deletions

diff --git a/src/pkg/malloc/malloc.go b/src/pkg/malloc/malloc.go
index 838b92f5f..66708a680 100644
--- a/src/pkg/malloc/malloc.go
+++ b/src/pkg/malloc/malloc.go
@@ -6,6 +6,9 @@
 // The actual functions are written in C
 // and part of the runtime library.
 
+// The malloc package exposes statistics and other low-level details about
+// the run-time memory allocator and collector.  It is intended for debugging
+// purposes only; other uses are discouraged.
 package malloc
 
 type Stats struct {