Fix win32 build

The types size_t and ssize_t are defined on Windows (in MSYS2), so there
is no need to typedef SIZE_T and SSIZE_T.

Exit code is "unsigned long" both on Windows 32 and 64 bits.

See <https://github.com/Genymobile/scrcpy/issues/46#issuecomment-373603596>.

app/src/command.h

@@ -7,12 +7,11 @@
 
 // <https://stackoverflow.com/a/44383330/1987178>
 #ifdef _WIN32
+# define PRIexitcode "lu"
 # ifdef _WIN64
 #   define PRIsizet PRIu64
-#   define PRIexitcode "lu"
 # else
 #   define PRIsizet PRIu32
-#   define PRIexitcode "u"
 # endif
 #else
 # define PRIsizet "zu"

app/src/net.h

@@ -9,8 +9,6 @@
   #define SHUT_RD SD_RECEIVE
   #define SHUT_WR SD_SEND
   #define SHUT_RDWR SD_BOTH
-  typedef SIZE_T size_t;
-  typedef SSIZE_T ssize_t;
   typedef SOCKET socket_t;
 #else
 # include <sys/socket.h>