Fix -Wshadow warnings in mingw builds.

Reviewed-by: Rich Salz <rsalz@openssl.org>

apps/speed.c

diff --git a/apps/speed.c b/apps/speed.c
index 4b53f61..046c0b2 100644
--- a/apps/speed.c
+++ b/apps/speed.c
@@ -297,9 +297,9 @@
         schlock = 0;
         thr = CreateThread(NULL, 4096, sleepy, NULL, 0, NULL);
         if (thr == NULL) {
-            DWORD ret = GetLastError();
-            BIO_printf(bio_err, "unable to CreateThread (%d)", ret);
-            ExitProcess(ret);
+            DWORD err = GetLastError();
+            BIO_printf(bio_err, "unable to CreateThread (%lu)", err);
+            ExitProcess(err);
         }
         while (!schlock)
             Sleep(0);           /* scheduler spinlock */

crypto/rand/rand_win.c

diff --git a/crypto/rand/rand_win.c b/crypto/rand/rand_win.c
index e926429..a91014b 100644
--- a/crypto/rand/rand_win.c
+++ b/crypto/rand/rand_win.c
@@ -196,7 +196,7 @@
 
 int RAND_poll(void)
 {
-    MEMORYSTATUS m;
+    MEMORYSTATUS mst;
     HCRYPTPROV hProvider = 0;
     DWORD w;
     int good = 0;
@@ -558,8 +558,8 @@
     readtimer();
 
     /* memory usage statistics */
-    GlobalMemoryStatus(&m);
-    RAND_add(&m, sizeof(m), 1);
+    GlobalMemoryStatus(&mst);
+    RAND_add(&mst, sizeof(mst), 1);
 
     /* process ID */
     w = GetCurrentProcessId();