Rename async-io.c++ to async-io-unix.c++, in preparation for factoring out…

Rename async-io.c++ to async-io-unix.c++, in preparation for factoring out common bits from async-io-win32.c++.

c++/Makefile.am

@@ -232,7 +232,7 @@ libkj_async_la_SOURCES=                                        \
   src/kj/async.c++                                             \
   src/kj/async-unix.c++                                        \
   src/kj/async-win32.c++                                       \
-  src/kj/async-io.c++                                          \
+  src/kj/async-io-unix.c++                                     \
   src/kj/async-io-win32.c++                                    \
   src/kj/time.c++
 endif !LITE_MODE

c++/src/kj/CMakeLists.txt

@@ -92,7 +92,7 @@ install(FILES ${kj-test-compat_headers} DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}
 set(kj-async_sources
   async.c++
   async-unix.c++
-  async-io.c++
+  async-io-unix.c++
   time.c++
 )
 set(kj-async_headers

c++/src/kj/async-io-win32.c++

@@ -20,7 +20,7 @@
 // THE SOFTWARE.
 
 #if _WIN32
-// For Unix implementation, see async-io.c++.
+// For Unix implementation, see async-io-unix.c++.
 
 // Request Vista-level APIs.
 #define WINVER 0x0600