libiberty: Fix memory leak in ada_demangle when symbol cannot be demangled.

When a symbol cannot be demangled in ada_demangle a new demangled VEC
will be allocated without deleting the demangled VEC already in use.

Running testsuite/test-demangle under valgrind will show the leak for
this entry in testsuite/demangle-expected:

    # Elaborated flag (not demangled)
    --format=gnat
    x_E
    <x_E>

 11 bytes in 1 blocks are definitely lost in loss record 1 of 1
    at 0x4C27BE3: malloc (vg_replace_malloc.c:299)
    by 0x413FE7: xmalloc (xmalloc.c:148)
    by 0x4025EC: ada_demangle (cplus-dem.c:930)
    by 0x402C59: cplus_demangle (cplus-dem.c:892)
    by 0x400FEC: main (test-demangle.c:317)

libiberty/ChangeLog:

	* cplus-dem.c (ada_demangle): Initialize demangled to NULL and
	XDELETEVEC demangled when unknown.

From-SVN: r241760

libiberty/ChangeLog

+2016-10-31  Mark Wielaard  <mjw@redhat.com>
+
+	* cplus-dem.c (ada_demangle): Initialize demangled to NULL and
+	XDELETEVEC demangled when unknown.
+
 2016-09-19  Andrew Stubbs  <ams@codesourcery.com>
 
 	* pex-win32.c (argv_to_cmdline): Quote zero-length parameters.

libiberty/cplus-dem.c

@@ -911,7 +911,7 @@ ada_demangle (const char *mangled, int option ATTRIBUTE_UNUSED)
   int len0;
   const char* p;
   char *d;
-  char *demangled;
+  char *demangled = NULL;
   
   /* Discard leading _ada_, which is used for library level subprograms.  */
   if (strncmp (mangled, "_ada_", 5) == 0)
@@ -1156,6 +1156,7 @@ ada_demangle (const char *mangled, int option ATTRIBUTE_UNUSED)
   return demangled;
 
  unknown:
+  XDELETEVEC (demangled);
   len0 = strlen (mangled);
   demangled = XNEWVEC (char, len0 + 3);