Back to $ARCHS_STANDARD for iOS builds

Removes the “Release-64bit” build configuration.
With Xcode 5.1+, the regular iOS frameworks will include 64-bit.
With earlier Xcodes only 32-bit.
NOTE: This commit breaks the automated Jenkins build.
The build script will need to remove the steps to build with Release-64bit,
and to copy extra 64-bit frameworks.