Enables ASTs in the user program.  ASTs can be disabled during  a
     debugging  session  using the command "DISABLE AST", and they can
     be  re-enabled  using  the  command  "ENABLE  AST".   Temporarily
     disabling  ASTs  in  this  fashion  allows  the  user  to prevent
     interrupts from occuring while he is debugging a particular piece
     of code.

 Format

     ENABLE AST

     Example:

     DBG> SHOW AST
     ASTs are disabled
     DBG> ENAB AST
     DBG> SHOW AST
     ASTs are enabled