Handle newlines in cIniFile (#5447)

* Handle newlines during read and write in cIniFile

When reading the ini file, replace \n with newline. When writing,
replace the newline with \n.

* Use ReplaceString instead of regex in IniFile

* Update cIniFile description

* Removed duplicate variable

* Revert "Removed duplicate variable"

This reverts commit de11bac.

* Removed duplicate variable

Now without plugin changes

---------

Co-authored-by: x12xx12x <44411062+12xx12@users.noreply.github.com>

Server/Plugins/APIDump/APIDesc.lua

@@ -5375,6 +5375,10 @@ ValueName0=SomeOtherValue
 				insert values by hand. Then you can store the object's contents to a disk file using WriteFile(), or
 				just forget everything by destroying the object. Note that the file operations are quite slow.</p>
 				<p>
+				Cuberite will write the characters '\n' in place of line breaks in the values of the cIniFile when
+				it is being stored into a file. It will also replace '\n' with line breaks when it reads an INI
+				file.
+				<p>
 				For storing high-volume low-latency data, use the {{sqlite3}} class. For storing
 				hierarchically-structured data, use the XML format, using the LuaExpat parser in the {{lxp}} class.
 			]],

src/IniFile.cpp

@@ -147,6 +147,7 @@ bool cIniFile::ReadFile(const AString & a_FileName, bool a_AllowExampleRedirect)
 			{
 				valuename = line.substr(0, pLeft);
 				value = TrimString(line.substr(pLeft + 1));
+				ReplaceString(value, "\\n", "\n");
 				AddValue(keyname, valuename, value);
 				break;
 			}
@@ -191,6 +192,7 @@ bool cIniFile::WriteFile(const AString & a_FileName) const
 	// Normally you would use ofstream, but the SGI CC compiler has
 	// a few bugs with ofstream. So ... fstream used.
 	fstream f;
+	AString writevalue;
 
 	f.open((a_FileName).c_str(), ios::out);
 	if (f.fail())
@@ -223,7 +225,9 @@ bool cIniFile::WriteFile(const AString & a_FileName) const
 		// Values.
 		for (size_t valueID = 0; valueID < m_Keys[keyID].m_Names.size(); ++valueID)
 		{
-			f << m_Keys[keyID].m_Names[valueID] << '=' << m_Keys[keyID].m_Values[valueID] << iniEOL;
+			writevalue = m_Keys[keyID].m_Values[valueID];
+			ReplaceString(writevalue, "\n", "\\n");
+			f << m_Keys[keyID].m_Names[valueID] << '=' << writevalue << iniEOL;
 		}
 		f << iniEOL;
 	}