cleanup programs

Clean up the contents of programs, add more guards to includes, move all
defines to the top of the top of files, remove some unused includes
diff --git a/programs/hash/hello.c b/programs/hash/hello.c
index 7c0546e..384ade1 100644
--- a/programs/hash/hello.c
+++ b/programs/hash/hello.c
@@ -29,12 +29,13 @@
 #if defined(POLARSSL_PLATFORM_C)
 #include "polarssl/platform.h"
 #else
+#include <stdio.h>
 #define polarssl_printf     printf
 #endif
 
-#include <stdio.h>
-
+#if defined(POLARSSL_MD5_C)
 #include "polarssl/md5.h"
+#endif
 
 #if !defined(POLARSSL_MD5_C)
 int main( int argc, char *argv[] )