add some preprocessor defines to make checks easy
replace tabs with spaces in Android.mk
add android-amazon implementation of avalon::GameCenter
fix GameCenter stubs for android-google and -samsung
ensure manager and manager->delegate are not NULL in ios payment backend

also it's important to NOT call finishTransaction if we're unable to
call onHasBeenPurchased() for the given product! it's okay if the delegate
it not set -- that's the will of the developer -- but in all other cases
something is wrong and we must ignore this transaction. it's the best behaviour
for the customer as apple will resend the transaction eventually.
globalManager pointer must be checked as it could be NULL
showAchievements and showScores now returns a boolean
ignore products with no type
fix detection of productId key for the current platform
don't pass NULL to addProduct() on invalid types
refactor detectProductId() a little bit
Merge pull request #22 from michaelcontento/preprocessor-helper-for-platform-checks

add some preprocessor defines to make checks easy
Merge pull request #23 from michaelcontento/amazon-gamecenter

[Android] Amazon GameCenter
Merge pull request #24 from michaelcontento/ios-payment-pointer-checks

[iOS] add a bunch of security checks to the payment backend
Merge pull request #25 from michaelcontento/android-payment-pointer-checks

[Android] globalManager pointer must be checked as it could be NULL
Merge pull request #26 from michaelcontento/fix-gamecenter-for-google-and-samsung

[Android] showAchievements and showScores now returns a boolean
Merge pull request #27 from michaelcontento/fix-payment-loader-platform-id-selection

[Android] Fix platformId selection in payment::Loader