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
Simplify build instructions
Display unknown commands received.
Update OS X build instructions

Update OpenSSL version
Homebrew is now the preferred dependancy manager
Replace HexBits with strprintf
Add note about PPA to build instructions
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 #4435

92ddf2c Update OS X build instructions (Michael Ford)
Merge pull request #4422

645d497 Replace HexBits with strprintf (jtimon)
Merge pull request #4418

d618965 Add note about PPA to build instructions (Drak)
e5f0247 Simplify build instructions (Drak)
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)
Make CBlockIndex a subclass of CBlockHeader
Unify CBlockHeader::hashPrevBlock and CDiskBlockIndex::hashPrev
Unify GetHash() and GetBlockHash()
Remove GetBlockHeader()