basic/selinux: work around mallinfo deprecation

Latest glibc has deprecated mallinfo(), so it might become unavailable at some point
in the future. There is malloc_info(), but it returns XML, ffs. I think the information
that we get from mallinfo() is quite useful, so let's use mallinfo() if available, and
not otherwise.

src/basic/macro.h

@@ -93,6 +93,10 @@
 #endif
 
 /* Temporarily disable some warnings */
+#define DISABLE_WARNING_DEPRECATED_DECLARATIONS                         \
+        _Pragma("GCC diagnostic push");                                 \
+        _Pragma("GCC diagnostic ignored \"-Wdeprecated-declarations\"")
+
 #define DISABLE_WARNING_FORMAT_NONLITERAL                               \
         _Pragma("GCC diagnostic push");                                 \
         _Pragma("GCC diagnostic ignored \"-Wformat-nonliteral\"")