Reported by the new script 'scripts/copyright.pl'. The script has a
regex whitelist for the files that don't need copyright headers.
Removed three (mostly usesless) README files from docs/
Closes#5141
long is 32 bits while size_t is 64 bits on MinGW-w64, so
typecheck-gcc.h complains when using size_t for a long option.
Also, curl_socket_t is unsigned long long rather than int.
Make the HTTP headers separated by default for improved security and
reduced risk for information leakage.
Bug: http://curl.haxx.se/docs/adv_20150429.html
Reported-by: Yehezkel Horowitz, Oren Souroujon
