Backport r62627 + r62744 from trunk to fix issue 2632.
- Issue #2632: Prevent socket.read(bignumber) from over allocating memory
  in the common case when the data is returned from the underlying socket
  in increments much smaller than bignumber.
diff --git a/Misc/NEWS b/Misc/NEWS
index c8fbedf..c5cf068 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -102,6 +102,9 @@
   stdout and stderr fds rather than leaving them open until the
   instance is destroyed.
 
+- Issue #2632: Prevent socket.read(bignumber) from over allocating memory
+  in the common case when the data is returned from the underlying socket
+  in increments much smaller than bignumber.
 
 Extension Modules
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