e_os.h does not belong with the exported headers.  Do not put it there
and make all files the depend on it include it without prefixing it
with openssl/.

This means that all Makefiles will have $(TOP) as one of the include
directories.

ssl/ssl_task.c

diff --git a/ssl/ssl_task.c b/ssl/ssl_task.c
index cac701a..e36af0e 100644
--- a/ssl/ssl_task.c
+++ b/ssl/ssl_task.c
@@ -124,7 +124,7 @@
 #include <string.h>		/* from ssltest.c */
 #include <errno.h>
 
-#include "openssl/e_os.h"
+#include "e_os.h"
 
 #include <openssl/buffer.h>
 #include <openssl/x509.h>