Move implementations from impl/*.h to *_impl.h #2

1. 
   sipa commented at 0:19 am on March 7, 2014: contributor

   Seems some tools get confused by identical file names.
2. 
   gmaxwell commented at 1:16 am on March 7, 2014: contributor

   I whined about this, so I think it’s a good change. Somehow the less deep nesting seems cleaner to me, but perhaps I’m weird. :)
3. 
   laanwj commented at 7:56 am on March 7, 2014: member

   Yeah why not, ACK
4. Move implementations from impl/*.h to *_impl.h 11ab562203
5. sipa referenced this in commit 8b3263b638 on Mar 12, 2014
6. sipa merged this on Mar 12, 2014
7. sipa closed this on Mar 12, 2014

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8. gmaxwell cross-referenced this on Mar 4, 2019 from issue Allow to use external default callbacks by real-or-random
9. benma referenced this in commit dd7379cb57 on Jul 15, 2019

Contributors
sipa gmaxwell laanwj