Move sysdeps_win32 to C++.

Change-Id: I27ca41b64d62bb3611b3a39a5c3bb4377d0773bc
diff --git a/adb/commandline.cpp b/adb/commandline.cpp
index 34efefe..19a2fee 100644
--- a/adb/commandline.cpp
+++ b/adb/commandline.cpp
@@ -249,11 +249,9 @@
 
 #if defined(_WIN32)
 
-// Implemented in sysdeps_win32.c.
-extern "C" {
+// Implemented in sysdeps_win32.cpp.
 void stdin_raw_init(int fd);
 void stdin_raw_restore(int fd);
-}
 
 #else
 static termios g_saved_terminal_state;