dbwrapper: Remove throw keywords in function signatures

Using throw() specifications in function signatures is not only
not required in C++, it is considered deprecated for
[various reasons](https://stackoverflow.com/questions/1055387/throw-keyword-in-functions-signature).
It is not implemented by any of the common C++ compilers. The usage is
also inconsistent with the rest of the source code.

src/dbwrapper.cpp

@@ -15,7 +15,7 @@
 #include <memenv.h>
 #include <stdint.h>
 
-void HandleError(const leveldb::Status& status) throw(dbwrapper_error)
+void HandleError(const leveldb::Status& status)
 {
     if (status.ok())
         return;
@@ -102,7 +102,7 @@ CDBWrapper::~CDBWrapper()
     options.env = NULL;
 }
 
-bool CDBWrapper::WriteBatch(CDBBatch& batch, bool fSync) throw(dbwrapper_error)
+bool CDBWrapper::WriteBatch(CDBBatch& batch, bool fSync)
 {
     leveldb::Status status = pdb->Write(fSync ? syncoptions : writeoptions, &batch.batch);
     HandleError(status);

src/dbwrapper.h

@@ -23,7 +23,7 @@ class dbwrapper_error : public std::runtime_error
     dbwrapper_error(const std::string& msg) : std::runtime_error(msg) {}
 };
 
-void HandleError(const leveldb::Status& status) throw(dbwrapper_error);
+void HandleError(const leveldb::Status& status);
 
 /** Batch of changes queued to be written to a CDBWrapper */
 class CDBBatch
@@ -180,7 +180,7 @@ class CDBWrapper
     ~CDBWrapper();
 
     template <typename K, typename V>
-    bool Read(const K& key, V& value) const throw(dbwrapper_error)
+    bool Read(const K& key, V& value) const
     {
         CDataStream ssKey(SER_DISK, CLIENT_VERSION);
         ssKey.reserve(ssKey.GetSerializeSize(key));
@@ -206,15 +206,15 @@ class CDBWrapper
     }
 
     template <typename K, typename V>
-    bool Write(const K& key, const V& value, bool fSync = false) throw(dbwrapper_error)
+    bool Write(const K& key, const V& value, bool fSync = false)
     {
         CDBBatch batch(&obfuscate_key);
         batch.Write(key, value);
         return WriteBatch(batch, fSync);
     }
 
     template <typename K>
-    bool Exists(const K& key) const throw(dbwrapper_error)
+    bool Exists(const K& key) const
     {
         CDataStream ssKey(SER_DISK, CLIENT_VERSION);
         ssKey.reserve(ssKey.GetSerializeSize(key));
@@ -233,22 +233,22 @@ class CDBWrapper
     }
 
     template <typename K>
-    bool Erase(const K& key, bool fSync = false) throw(dbwrapper_error)
+    bool Erase(const K& key, bool fSync = false)
     {
         CDBBatch batch(&obfuscate_key);
         batch.Erase(key);
         return WriteBatch(batch, fSync);
     }
 
-    bool WriteBatch(CDBBatch& batch, bool fSync = false) throw(dbwrapper_error);
+    bool WriteBatch(CDBBatch& batch, bool fSync = false);
 
     // not available for LevelDB; provide for compatibility with BDB
     bool Flush()
     {
         return true;
     }
 
-    bool Sync() throw(dbwrapper_error)
+    bool Sync()
     {
         CDBBatch batch(&obfuscate_key);
         return WriteBatch(batch, true);