On HPUX-aCC, readdir_r is only declared if the option '-mt' is passed onto the aCC

compiler. Now the code detects if the multithreading option is passed by
checking if _REENTRANT is defined (in combination with __HP_aCC)


[SVN r29728]

libs/filesystem

@@ -1 +1 @@
-Subproject commit 05df06a5c98adb87ce43b850cc64bbe1b871ac12
+Subproject commit 348391a38a2fa4162862c82211b14a112ce1f1b4