BIND 10 #383: Generalize IOService constructor

[BIND 10 Development]

#383: Generalize IOService constructor
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      Reporter:  jelte        |        Owner:  jelte
          Type:  enhancement  |       Status:  new  
      Priority:  major        |    Milestone:       
     Component:  recurser     |   Resolution:       
      Keywords:               |    Sensitive:  0    
Estimatedhours:  0.0          |        Hours:  0    
      Billable:  1            |   Totalhours:  0    
      Internal:  0            |  
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Comment(by jelte):

 Ok, I made the proposed change in r3305 and r3306.

 IOService still uses that Impl pattern (so other code does not have to
 (indirectly) include asio/io_service.hpp), and I now wonder whether
 DNSService (which is mostly the old IOService without the IOService-
 specific function (i.e. run(), stop() etc.) still needs to do the same.

 It doesn't for the sake op asio::io_service, but it currently uses those
 internal/*dns.h headers, which would then need to become public. Should we
 leave this as it is?

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Ticket URL: <https://bind10.isc.org/ticket/383#comment:2>
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