dict/dict: Fix memory leaks at program termination

Avoid dynamic memory allocation for the static variable 'cache'.
Now the destructor for that variable is called automatically
when Tesseract terminates and releases all associated memory.

Signed-off-by: Stefan Weil <sw@weilnetz.de>

dict/dict.cpp

@@ -184,11 +184,10 @@ Dict::~Dict() {
 }
 
 DawgCache *Dict::GlobalDawgCache() {
-  // We dynamically allocate this global cache (a singleton) so it will outlive
-  // every Tesseract instance (even those that someone else might declare as
-  // global statics).
-  static DawgCache *cache = new DawgCache();  // evil global singleton
-  return cache;
+  // This global cache (a singleton) will outlive every Tesseract instance
+  // (even those that someone else might declare as global statics).
+  static DawgCache cache;
+  return &cache;
 }
 
 void Dict::Load(DawgCache *dawg_cache) {