Include process.h for _getpid on windows.
Previously the test programmes happened to link because _getpid
returns an int, which is the default prototype. Instead, include
the appropriate header to supply a real declaration, fixing the
associated warning.
I moved the getpid->_getpid define to the site of the header
inclusion to make clear what's going on, rather than have it
floating in win32/config.h.
diff --git a/tests/test_opus_decode.c b/tests/test_opus_decode.c
index 2c6a872..868869b 100644
--- a/tests/test_opus_decode.c
+++ b/tests/test_opus_decode.c
@@ -38,6 +38,9 @@
#include <time.h>
#if (!defined WIN32 && !defined _WIN32) || defined(__MINGW32__)
#include <unistd.h>
+#else
+#include <process.h>
+#define getpid _getpid
#endif
#include "opus.h"
#include "test_opus_common.h"