emulator: opengl: Make render_api.h C-compatible

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

tools/emulator/opengl/host/libs/libOpenglRender/render_api.cpp

@@ -14,6 +14,7 @@
 * limitations under the License.
 */
 #include "libOpenglRender/render_api.h"
+#include "IOStream.h"
 #include "FrameBuffer.h"
 #include "RenderServer.h"
 #include "osProcess.h"
@@ -23,6 +24,8 @@ static osUtils::childProcess *s_renderProc = NULL;
 static RenderServer *s_renderThread = NULL;
 static int s_renderPort = 0;
 
+static IOStream *createRenderThread(int p_stream_buffer_size);
+
 #ifdef __APPLE__
 #define  RENDER_API_USE_THREAD
 #endif