Release notes for ABCL 0.16

Improved THE type checking
The compiler outputs type checks for simple enough types at *safety* levels 1 and 2 now.
The interpreter checks simple enough types at all *safety* levels
ANSI test fixes
Fixed tests due to better initarg checking:
Added JVM threading primitives
SYNCHRONIZED-ON, OBJECT-NOTIFY, OBJECT-NOTIFY-ALL equivalents of the Java synchronized block, Object.notify() and Object.notifyAll()
New THREADS package to hold threading primitives
The symbols are retained in the old EXTENSIONS package until 0.22
Type checking for structure slot accessor functions
The generated accessor functions for structure slots now assert the type of the argument passed in using a THE form
Fixed breakage when combining the pretty printer and Gray streams
The fixes mean changes to the generic functions in Gray streams to compensate for the fact that the pretty printer wraps streams.
Various performance improvements

Release notes for older releases.