On very resource constraind devices you need to be able to
control the size of all buffers and structures placed on the
stack.

Conditionally include dirent.h and dlfcn.h

If you do not have a filesystem or do not support dav or
dynamic loading, the corresponding header files need not
be included (some environments might not have them).

Added #define's for deprecated POSIX names

make compile with g++ (fix invalid cast from ‘void*’)

transmit http answer code using http_client