cleanup: make local functions static

urlapi: turn three local-only functions into statics

conncache: make conncache_find_first_connection static

multi: make detach_connnection static

connect: make getaddressinfo static

curl_ntlm_core: make hmac_md5 static

http2: make two functions static

http: make http_setup_conn static

connect: make tcpnodelay static

tests: make UNITTEST a thing to mark functions with, so they can be static for
normal builds and non-static for unit test builds

... and mark Curl_shuffle_addr accordingly.

url: make up_free static

setopt: make vsetopt static

curl_endian: make write32_le static

rtsp: make rtsp_connisdead static

warnless: remove unused functions

memdebug: remove one unused function, made another static