Update to each layer of JPDA spec (JDI, JDWP, JVMDI) to reflect that native
frames cannot not be popped or popped to (new top frame cannot be native)
was poorly executed, the result is that it is clear that native frames
cannot be popped but not clear that they cannot be popped to.

As a result NSK test popframe004 was written in apparent comformance to the
spec but yet fails.

Name: elR10090 Date: 09/23/2001


This bug affects the following test from testbase_nsk:
    nsk/jvmdi/PopFrame/popframe004

Pavel N. Visotsky, ###@###.###
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