Added support for if statement.

Added if statement support but realized that my register allocation
stuff is totally hosed and needs to be fixed.  That will be done in the
next check in. Actually I'll branch on that one.

 On branch p3_stage_2
 Changes to be committed:

	modified:   .gitignore
	modified:   CodeGenerator.C
	modified:   CodeGenerator.H
	modified:   ice9.y