make all catch() arguments const

- I saw this on http://en.cppreference.com/w/cpp/language/try_catch and
  thought it would be a good idea
- also unify used format to better be able to search for exception
  uses in our codebase

src/util.h

@@ -84,7 +84,7 @@ static inline bool error(const char* format)
     return false;
 }
 
-void PrintExceptionContinue(std::exception* pex, const char* pszThread);
+void PrintExceptionContinue(const std::exception *pex, const char* pszThread);
 void ParseParameters(int argc, const char*const argv[]);
 void FileCommit(FILE *fileout);
 bool TruncateFile(FILE *file, unsigned int length);
@@ -186,12 +186,12 @@ template <typename Callable> void LoopForever(const char* name,  Callable func,
             func();
         }
     }
-    catch (boost::thread_interrupted)
+    catch (const boost::thread_interrupted&)
     {
         LogPrintf("%s thread stop\n", name);
         throw;
     }
-    catch (std::exception& e) {
+    catch (const std::exception& e) {
         PrintExceptionContinue(&e, name);
         throw;
     }
@@ -214,12 +214,12 @@ template <typename Callable> void TraceThread(const char* name,  Callable func)
         func();
         LogPrintf("%s thread exit\n", name);
     }
-    catch (boost::thread_interrupted)
+    catch (const boost::thread_interrupted&)
     {
         LogPrintf("%s thread interrupt\n", name);
         throw;
     }
-    catch (std::exception& e) {
+    catch (const std::exception& e) {
         PrintExceptionContinue(&e, name);
         throw;
     }