Enable -Wmissing-variable-declarations and
-Wincompatible-pointer-types-discards-qualifiers (the latter did not require
any code changes).

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

crypto/sec_mem.c

diff --git a/crypto/sec_mem.c b/crypto/sec_mem.c
index fbed8b4..b7a9d3b 100644
--- a/crypto/sec_mem.c
+++ b/crypto/sec_mem.c
@@ -31,7 +31,7 @@
 #endif
 
 #ifdef IMPLEMENTED
-size_t secure_mem_used;
+static size_t secure_mem_used;
 
 static int secure_mem_initialized;
 static int too_late;