Use new parser code in proxy_dll

- injected_api.h gets included from a shared path now, no need to
manually sync anymore
- renamed iaout, iain to ia_client and ia_server (ia means injected
API). both client and server have i/o, so this naming is more logical)
- i guess i found a bug in the VC linker? it somehow doesn't link the
ia_server code if I include the header file. cheap workaround: include
the .c file.
- in the server code, we grab the 'header' byte outside of the parser
function. i've adjusted the client code accordingly.