Change 'false' to 'False' in pmml_compiler.drl.

Nearly all tests (148 of 151) in drools-pmml fail for me (Mac OS X Mountain Lion - JDK 1.6) with error messages like this:
```
testFunctionsNested(org.drools.pmml.pmml_4_1.transformations.UserDefinedFunctionsTest)  Time elapsed: 0.604 sec  <<< ERROR!
java.lang.NoClassDefFoundError: org/dmg/pmml/pmml_4_1/descr/false (wrong name: org/dmg/pmml/pmml_4_1/descr/False)
	at java.lang.ClassLoader.defineClass1(Native Method)
```

By changing the 'false' value in a declare in pmml_compiler.drl to 'False' all tests but one (an apparently unrelated issue in SVMTest) pass.  I haven't any idea if this is the right way to fix this but thought I'd pass it along to save time in the event someone else runs into this.