add code in Lecture 18: Thread Safety.

Included are the following 10 files:

	Lectures/L18-Thread_Safety/code/lec18/.classpath
	Lectures/L18-Thread_Safety/code/lec18/.gitignore
	Lectures/L18-Thread_Safety/code/lec18/.project
	Lectures/L18-Thread_Safety/code/lec18/src/argument/Graph.java
	Lectures/L18-Thread_Safety/code/lec18/src/argument/MyString.java
	Lectures/L18-Thread_Safety/code/lec18/src/argument/MyString2.java
	Lectures/L18-Thread_Safety/code/lec18/src/argument/StringBuffer.java
	Lectures/L18-Thread_Safety/code/lec18/src/confinement/Factorial.java
	Lectures/L18-Thread_Safety/code/lec18/src/confinement/PinballSimulator.java
	Lectures/L18-Thread_Safety/code/lec18/src/confinement/Prime.java

Thank you!
							Lawrence X. Amlord
							  Nov. 15th, 2014
							   Xi'an, China
initialize the editor example in Lecture 20: Queues and Locks.

Included are the following 10 files:

	Lectures/L20-Queues_&_Locks/code/ex20-editor/.classpath
	Lectures/L20-Queues_&_Locks/code/ex20-editor/.gitignore
	Lectures/L20-Queues_&_Locks/code/ex20-editor/.project
	Lectures/L20-Queues_&_Locks/code/ex20-editor/src/editor/EditBuffer.java
	Lectures/L20-Queues_&_Locks/code/ex20-editor/src/editor/EditBufferTest.java
	Lectures/L20-Queues_&_Locks/code/ex20-editor/src/editor/Editor.java
	Lectures/L20-Queues_&_Locks/code/ex20-editor/src/editor/GapBuffer.java
	Lectures/L20-Queues_&_Locks/code/ex20-editor/src/editor/GapBufferTest.java
	Lectures/L20-Queues_&_Locks/code/ex20-editor/src/editor/SimpleBuffer.java
	Lectures/L20-Queues_&_Locks/code/ex20-editor/src/editor/SimpleBufferTest.java

Thank you!
							Lawrence X. Amlord
							  Nov. 22nd, 2014
							   Xi'an, China