Add support for character encodings

Previous commit added support of it to Csocket.
When encoding is specified, core will convert incoming messages to UTF-8,
and outgoing messages from UTF-8.
When no encoding is specified, it will do nothing to bytes, like before.
This is to be changed somewhere in future, to have UTF-8 on wire by
default too.
When encoding's name starts with *, incoming messages will be treated as
UTF-8, if it is already correct UTF-8. Otherwise, it's converted.

Fix #151
Fix #366

include/znc/IRCNetwork.h

@@ -141,12 +141,14 @@ public:
 	const CString& GetIdent(const bool bAllowDefault = true) const;
 	const CString& GetRealName() const;
 	const CString& GetBindHost() const;
+	const CString& GetEncoding() const;
 
 	void SetNick(const CString& s);
 	void SetAltNick(const CString& s);
 	void SetIdent(const CString& s);
 	void SetRealName(const CString& s);
 	void SetBindHost(const CString& s);
+	void SetEncoding(const CString& s);
 
 	double GetFloodRate() const { return m_fFloodRate; }
 	unsigned short int GetFloodBurst() const { return m_uFloodBurst; }
@@ -167,6 +169,7 @@ protected:
 	CString            m_sIdent;
 	CString            m_sRealName;
 	CString            m_sBindHost;
+	CString            m_sEncoding;
 
 	CModules*          m_pModules;
 

include/znc/Socket.h

@@ -30,6 +30,11 @@ public:
 	~CZNCSock() {}
 
 	virtual int ConvertAddress(const struct sockaddr_storage * pAddr, socklen_t iAddrLen, CS_STRING & sIP, u_short * piPort);
+
+#ifndef HAVE_ICU
+	// Don't fail to compile when ICU is not enabled
+	void SetEncoding(const CString&) {}
+#endif
 };
 
 enum EAddrType {

include/znc/User.h

@@ -120,6 +120,7 @@ public:
 	void SetDenySetBindHost(bool b);
 	bool SetStatusPrefix(const CString& s);
 	void SetDefaultChanModes(const CString& s);
+	void SetClientEncoding(const CString& s);
 	void SetQuitMsg(const CString& s);
 	bool AddCTCPReply(const CString& sCTCP, const CString& sReply);
 	bool DelCTCPReply(const CString& sCTCP);
@@ -153,6 +154,7 @@ public:
 	const CString& GetPassSalt() const;
 	const std::set<CString>& GetAllowedHosts() const;
 	const CString& GetTimestampFormat() const;
+	const CString& GetClientEncoding() const;
 	bool GetTimestampAppend() const;
 	bool GetTimestampPrepend() const;
 
@@ -192,6 +194,7 @@ protected:
 	CString               m_sPassSalt;
 	CString               m_sStatusPrefix;
 	CString               m_sDefaultChanModes;
+	CString               m_sClientEncoding;
 
 	CString               m_sQuitMsg;
 	MCString              m_mssCTCPReplies;