Remove static buffers from StringHelpers to prevent overwriting strings from another thread.

Minecraft.World/FileInputStream.cpp

@@ -18,7 +18,7 @@
 //SecurityException - if a security manager exists and its checkRead method denies read access to the file.
 FileInputStream::FileInputStream(const File &file)
 {
-	const char *pchFilename=wstringtofilename(file.getPath());
+	std::string pchFilename=wstringtofilename(file.getPath());
 #ifdef _UNICODE
 	m_fileHandle = CreateFile(
 		file.getPath().c_str(), // file name
@@ -31,7 +31,7 @@ FileInputStream::FileInputStream(const File &file)
 		);
 #else
 	m_fileHandle = CreateFile(
-		pchFilename, // file name
+		pchFilename.c_str(), // file name
 		GENERIC_READ, // access mode
 		0, // share mode // TODO 4J Stu - Will we need to share file? Probably not but...
 		nullptr, // Unused