Add missing header for gcc3

When include/linux/compiler.h is included, the associated gcc3
header is required for older build environments.
Signed-off-by: NScott McNutt <smcnutt@psyent.com>
Acked-by: NMike Frysinger <vapier@gentoo.org>

include/linux/compiler-gcc3.h

+#ifndef __LINUX_COMPILER_H
+#error "Please don't include <linux/compiler-gcc3.h> directly, include <linux/compiler.h> instead."
+#endif
+
+#if __GNUC_MINOR__ >= 3
+# define __used			__attribute__((__used__))
+#else
+# define __used			__attribute__((__unused__))
+#endif
+
+#if __GNUC_MINOR__ >= 4
+#define __must_check		__attribute__((warn_unused_result))
+#endif
+
+/*
+ * A trick to suppress uninitialized variable warning without generating any
+ * code
+ */
+#define uninitialized_var(x) x = x
+
+#define __always_inline		inline __attribute__((always_inline))