Fix compile error on Mac OS X 10.6:

error: implicit declaration of function 'ERROR_dictionary' is invalid in C99

https://github.com/att/ast/issues/1462
https://github.com/att/ast/pull/1465/commits/f8290d2acc133953fce4e643a44c88821797add0
--- src/lib/libdll/dlfcn.c.orig
+++ src/lib/libdll/dlfcn.c
@@ -34,7 +34,9 @@
 //
 void do_not_use_this_dlfcn() { abort(); }
 
-#define T(x) ERROR_dictionary(x)
+#ifndef ERROR_dictionary
+#define ERROR_dictionary(s) (s)
+#endif
 
 #if !_hdr_dlfcn || !_lib_dlopen
 #if _hdr_dl
@@ -284,11 +286,11 @@ typedef struct Dll_s {
 
 static const char *dlmessage = "no error";
 
-static const char e_cover[] = T("cannot access covered library");
-static const char e_handle[] = T("invalid handle");
-static const char e_space[] = T("out of space");
-static const char e_static[] = T("image statically linked");
-static const char e_undefined[] = T("undefined symbol");
+static const char e_cover[] = ERROR_dictionary("cannot access covered library");
+static const char e_handle[] = ERROR_dictionary("invalid handle");
+static const char e_space[] = ERROR_dictionary("out of space");
+static const char e_static[] = ERROR_dictionary("image statically linked");
+static const char e_undefined[] = ERROR_dictionary("undefined symbol");
 
 static Dll_t global = {DL_MAGIC};