Support double hashtags (and double mentions) in newpostmsg

See https://github.com/miguelfreitas/twister-html/commit/706f17869bcb59200b9247df187a54dd52990720 (https://github.com/miguelfreitas/twister-html/pull/202) and https://github.com/miguelfreitas/twister-core/commit/07edcd08a9e5c43c6442b9c8d65cf9b44b2cfd9e (https://github.com/miguelfreitas/twister-core/pull/295)
Update twister.cpp
Process "Connection: close" header in non-JSON requests
fix asserts to support NDEBUG
enable NDEBUG define
Merge pull request #298 from dryabov/patch-7

Support double hashtags (and double mentions) in newpostmsg
Merge pull request #299 from dryabov/patch-8

Process "Connection: close" header in non-JSON requests
Merge pull request #300 from dryabov/bitcoin-ndebug

Fix support of NDEBUG