Rescue IO::WaitReadable instead of EAGAIN for blocking read

On Windows, `read_nonblock` raises `Errno::EWOULDBLOCK` if a blocking read would occur, which is a different value from `Errno::EAGAIN`. Both of these errors are extended by `IO::WaitReadable` which is Ruby's recommended exception class for retrying `read_nonblock`.

lib/puma/client.rb

@@ -153,7 +153,7 @@ def try_to_finish
 
       begin
         data = @io.read_nonblock(CHUNK_SIZE)
-      rescue Errno::EAGAIN
+      rescue IO::WaitReadable
         return false
       rescue SystemCallError, IOError, EOFError
         raise ConnectionError, "Connection error detected during read"
@@ -349,7 +349,7 @@ def read_body
 
       begin
         chunk = @io.read_nonblock(want)
-      rescue Errno::EAGAIN
+      rescue IO::WaitReadable
         return false
       rescue SystemCallError, IOError
         raise ConnectionError, "Connection error detected during read"