Add :plc target to build the full compiler JAR

Having a single combined JAR makes it easier to run the compiler
from the command line for testing.

Change-Id: I8dc88608b1018c117fcae122677ee8530ab95a94

BUCK

diff --git a/BUCK b/BUCK
index 07eb695..a843f8e 100644
--- a/BUCK
+++ b/BUCK
@@ -103,6 +103,12 @@
 )
 
 java_binary(
+  name = 'plc',
+  main_class = 'com.googlecode.prolog_cafe.compiler.Compiler',
+  deps = [':compiler'],
+)
+
+java_binary(
   name = 'cafeteria',
   main_class = 'com.googlecode.prolog_cafe.repl.PrologMain',
   deps = [':cafeteria_lib'],