Use #ifdef, not #if

This commit was SVN r14439.

ompi/tools/ompi_info/ompi_info.cc

@@ -23,13 +23,13 @@
 
 #include <stdio.h>
 #include <ctype.h>
-#if HAVE_UNISTD_H
+#ifdef HAVE_UNISTD_H
 #include <unistd.h>
 #endif
-#if HAVE_NETDB_H
+#ifdef HAVE_NETDB_H
 #include <netdb.h>
 #endif
-#if HAVE_SYS_PARAM_H
+#ifdef HAVE_SYS_PARAM_H
 #include <sys/param.h>
 #endif
 #include <errno.h>