Use POSIX macros for linux

cde/lib/DtSvc/DtUtil1/DtsInit.c

@@ -73,7 +73,7 @@
 #include <Dt/Dts.h>
 #include "DtSvcLock.h"
 
-#if !defined(linux)
+#if !defined(__linux__)
 extern char	*strdup(const char *);
 #endif
 

cde/lib/DtSvc/DtUtil1/DtsSort.c

@@ -58,7 +58,7 @@
 #include "Dt/DtsDb.h"
 #include "Dt/Dts.h"
 
-#if !defined(linux)
+#if !defined(__linux__)
 extern	char	*strdup(const char *);
 #endif
 

cde/lib/DtSvc/DtUtil1/Saver.c

@@ -167,7 +167,7 @@ _DtSaverStart(
   */
   if (saver_list.serial == 0)
   {
-#if !defined(linux) && !defined(CSRG_BASED)
+#if !defined(__linux__) && !defined(CSRG_BASED)
     /* JET - how can this ever work anyway? */
     putenv(envdata);
     envdata[0] = '\0';
@@ -214,7 +214,7 @@ _DtSaverStart(
     sprintf(pe, " %lx", XtWindow(drawArea[i]));
   }
 
-#if defined(linux) || defined(CSRG_BASED)
+#if defined(__linux__) || defined(CSRG_BASED)
   putenv(envdata);
 #endif
 

cde/lib/DtSvc/DtUtil1/strtab.c

@@ -68,7 +68,7 @@ struct strtab_build {
 
 static void inc_it  (int * a, int * b, unsigned char * key);
 static void build_it(int a, struct strtab_build * ptr, unsigned char * key);
-#if !defined(linux)
+#if !defined(__linux__)
 extern char * strdup(const char *);
 #endif
 typedef	int (*des_func)(void *);