improve minilex use external parsing header

Clean up minilex
Move the header output to stdout
Introduce lexfile.h as the header output
Use lexfile.h in both minilex itself and lws
Add the following header support

       "Accept:",
       "If-Modified-Since:",
       "Accept-Encoding:",
       "Accept-Language:",
       "Pragma:",
       "Cache-Control:",
       "Authorization:",
       "Cookie:",
       "Content-Type:",
       "Date:",
       "Range:",
       "Referer:"

Signed-off-by: Andy Green <andy.green@linaro.org>
make ah available in http callback properly

Signed-off-by: Andy Green <andy.green@linaro.org>
allow other headers in http send file

Signed-off-by: Andy Green <andy.green@linaro.org>
add cookie example to test server

Signed-off-by: Andy Green <andy.green@linaro.org>