Make ECPG regression tests run with -c only for array_of_struct.pgc

on MSVC.

Fix strange nonstandard version of __stdcall specifyer in thread
tests on win32.

src/interfaces/ecpg/test/expected/thread-alloc.c

@@ -121,7 +121,7 @@ struct sqlca_t *ECPGget_sqlca(void);
 
 
 #ifdef WIN32
-static unsigned STDCALL fn(void* arg)
+static unsigned __stdcall fn(void* arg)
 #else
 static void* fn(void* arg)
 #endif