ensure clean and consistent "namespace" usage

- remove some missplaced ;
- ensure end of a namespace is clearly visible
- use same formatting when using namespace
update coding.md to reflect changes by pull

- also mention alphabetical include ordering
Display unknown commands received.
Correct comment for 15-of-15 p2sh script size

The original comment forgets to account for the script push which will
need an OP_PUSHDATA2 + 2-bytes for the 513 script bytes.

props davecgh
fixes #4224
Merge pull request #4398

86fe1b8 update coding.md to reflect changes by pull (Philip Kaufmann)
e10dcf2 ensure clean and consistent "namespace" usage (Philip Kaufmann)
Merge pull request #4425

6ecf3ed Display unknown commands received. (R E Broadley)
Merge pull request #4436

675bcd5 Correct comment for 15-of-15 p2sh script size (Michael Ford)