Fix problematic conditional build directives

Replace unfortunate "#if HAVE_<feature>" directives with probably
intended "#ifdef HAVE_<feature>" forms, or compilation may break if
./configure defines a HAVE_<feautre> but empty.

Signed-off-by: Janusz Krzysztofik <jkrzyszt@tis.icnet.pl>

cmd.c

@@ -1990,7 +1990,7 @@ void command_help ( char *command )
       display_gen_help(helpstate);
    }
 
-#if HAVE_FEATURE_RFXS
+#ifdef HAVE_FEATURE_RFXS
    if ( (list & HELP_STATE) || (list & HELP_RFXS) ) {
       /* RFXSensor state commands */
       printf("\n [RFXSensor state commands  (H = Housecode, u = Single unit) - require heyu engine]\n");

digimax.c

@@ -427,7 +427,7 @@ char *translate_digimax ( unsigned char *buf, unsigned char *sunchanged, int *la
 int show_digimax ( void )
 {
 
-#if HAVE_FEATURE_DMX
+#ifdef HAVE_FEATURE_DMX
    ALIAS         *aliasp;
    char          hc;
    int           unit, index, temp, count = 0, maxlabel = 0;