Revert "Rewrite the JOIN channel logic, dropping MaxJoins"

This reverts commit db7c47f97d.

Too many joined channels at once started to cause disconnect because of
"Max SendQ Exceeded", which is not much better than previous Flood.

Now MaxJoins is 0 by default, which preserves the current behavior of
joining all channels at once. If someone experiences those disconnects
due to SendQ, they can tune MaxJoins.

Fix #329

Conflicts:
	include/znc/User.h
	modules/controlpanel.cpp
	modules/webadmin.cpp
	src/User.cpp

include/znc/IRCNetwork.h

@@ -72,6 +72,7 @@ public:
 	bool AddChan(const CString& sName, bool bInConfig);
 	bool DelChan(const CString& sName);
 	void JoinChans();
+	void JoinChans(std::set<CChan*>& sChans);
 
 	const CString& GetChanPrefixes() const { return m_sChanPrefixes; };
 	void SetChanPrefixes(const CString& s) { m_sChanPrefixes = s; };

include/znc/User.h

@@ -124,6 +124,7 @@ public:
 	void SetTimestampPrepend(bool b) { m_bPrependTimestamp = b; }
 	void SetTimezone(const CString& s) { m_sTimezone = s; }
 	void SetJoinTries(unsigned int i) { m_uMaxJoinTries = i; }
+	void SetMaxJoins(unsigned int i) { m_uMaxJoins = i; }
 	void SetSkinName(const CString& s) { m_sSkinName = s; }
 	void SetMaxNetworks(unsigned int i) { m_uMaxNetworks = i; }
 	// !Setters
@@ -165,6 +166,7 @@ public:
 	unsigned long long BytesRead() const { return m_uBytesRead; }
 	unsigned long long BytesWritten() const { return m_uBytesWritten; }
 	unsigned int JoinTries() const { return m_uMaxJoinTries; }
+	unsigned int MaxJoins() const { return m_uMaxJoins; }
 	CString GetSkinName() const;
 	unsigned int MaxNetworks() const { return m_uMaxNetworks; }
 	// !Getters
@@ -212,6 +214,7 @@ protected:
 	unsigned long long    m_uBytesWritten;
 	unsigned int          m_uMaxJoinTries;
 	unsigned int          m_uMaxNetworks;
+	unsigned int          m_uMaxJoins;
 	CString               m_sSkinName;
 
 	CModules*             m_pModules;