Added check for /usr/libexec/java_home

This is the preferred way of choosing a JVM on OS X

http://developer.apple.com/library/mac/#qa/qa1170/_index.html
GROOVY-5632: Closure default params can cause BUG! exception in phase 'class generation'
Fast exit from loop in StaticTypeCheckingVisitor.inferReturnTypeGenerics
GROOVY-5863: ImportCustomizer for CompilerCustomizationBuilder is not added to configscript CompilerConfiguration
GROOVY-5868 - ConfigObject is unexpectedly no longer Cloneable
GROOVY-5370: ConfigSlurper - multiple environment blocks broken

All credit for the patch and tests to Richard Rattigan. I just created a pull request and did some minimal refactoring.
GROOVY-5761 - getBytes for GString
GROOVY-4670: groovy.ui.Console cannot be extended

https://jira.codehaus.org/browse/GROOVY-4670
GROOVY-4572: Provide File method to get directory size

https://jira.codehaus.org/browse/GROOVY-4572

Original patch created by Evgeny Goldin. I just ported the patch to 2.0 and did some minimal refactoring. All credit belongs to Evgeny Goldin.
GROOVY-5242: groovy.lang.Closure javadoc should mention method resolution in resolve strategy constants

https://jira.codehaus.org/browse/GROOVY-5242
Merge pull request #95 from PascalSchumacher/GROOVY-5370

GROOVY-5370: ConfigSlurper - multiple environment blocks broken
merged
use "clone.configFile = configFile" instead of "clone.configFile = new URL(configFile.toString());" because the clone of the backing map is shallow anyway
removed unnecessary import
Merge pull request #99 from PascalSchumacher/GROOVY-5761_GString_getBytes

GROOVY-5761 - getBytes for GString
merged
Merge pull request #94 from PascalSchumacher/GROOVY-5868

GROOVY-5868 - ConfigObject is unexpectedly no longer Cloneable
merged
GROOVY-5877: Provide a flag for the groovyc ant task to control whether it searches the classpath for source files (prefactoring work to clean up some flags that weren't being set properly and a couple of typos)
GROOVY-5877: Provide a flag for the groovyc ant task to control whether it searches the classpath for source files
Merge pull request #102 from PascalSchumacher/GROOVY-5242_Closure_javadoc_resolve_strategies

GROOVY-5242: groovy.lang.Closure javadoc should mention method resolution...
merged
Merge pull request #101 from PascalSchumacher/GROOVY-4572_File_directorySize

GROOVY-4572: Provide File method to get directory size
merged
Merge pull request #100 from PascalSchumacher/GROOVY-4670_UI_Console_cannot_be_extended

GROOVY-4670: groovy.ui.Console cannot be extended
merged