fix segfault in BuiltinElement::dispose

If a BuiltinElement is never used (i.e. we never try to load anything
from it), its init method will never be called, and thus its backing
library will never be loaded.  In that case, we should not try to call
library->disposeAll() in the destructor.
Merge pull request #336 from dicej/builtinelement-dispose

fix segfault in BuiltinElement::dispose
implement JVM_isNaN

This method was previously unimplemented and untested.  However, the
JMH benchmark suite requires it, so now it's time to implement it.
Merge pull request #337 from dicej/master

implement JVM_isNaN
abort if JIT triggered when AVIAN_AOT_ONLY is defined

If AVIAN_AOT_ONLY is defined and the VM is asked to compile a method
anyway, we should abort immediately rather than let it crash later
(e.g. due to an access violation on a non-jailbroken iPhone).  This
makes debugging such issues a bit easier since the failure will come
earlier and with a more obvious cause.
Merge pull request #339 from dicej/aotonly

abort if JIT triggered when AVIAN_AOT_ONLY is defined
Merge pull request #341 from joshuawarner32/master

Classpath native sources to depend on vm-depends in makefile (fixes #340)