This change modifies the function declarations under developement/tools/emulator/opengl/host/include/render_api.h to make them callable from C. This is preparation work for integrating the rendering library into the emulator. The plan is to dlopen() the library dynamically and using non-mangled function names makes using dlsym() both easier and more portable. Change-Id: I34656ea4618dbb989fb6ff78df43e9bfb38a7799