ignore flow control in h2 when sending first request

fix lalb be disabled wrongly

remove duplicate inline def in ssl_compat.h

remove ```#include wire_format_lite_inl.h```  fix Protobuf 3.8 build error

remove ```#include wire_format_lite_inl.h``` to fix Protobuf 3.8 build error 
test build ok with protobuf 3.6.1 and protobuf 3.8.0

Adapt to protobuf 3.7 & 3.8

Update license header to Apache

Add object_pool_unittest.cpp to unittest

nshead_message, serialized_request, thrift_message be independent
of protobuf.

fix build  scripts under mac os env and add building section for README