gnu.classpath.boot.library.path support in Runtime.java

[Robert Schuster]

Hello,
as discussed on IRC GNU Classpath I introduced a system property named 
gnu.classpath.boot.library.path which contains a path of directories 
where Classpath's native libraries are located.

It is optional for a runtime to support. Actually it depends on the VM's 
ability to run a non-default Classpath installation. By default the 
property is not set and so it won't cause any trouble. The proprietary 
VMs have a similar property but that is not a matter for us because the 
feature is not specified.

On IRC I was told that it is the VM's task to find a native library. 
However by looking in java.lang.Runtime I found a  piece of code that 
iterates through a String array of directory names. On each iteration it 
prepends a directory name to a library name and tries to load it. This 
array is created in the constructor of Runtime by evaluating the 
java.library.path property.
This algorithm is only used if a VM was not able to load a native 
library via VMRuntime.nativeLoad().

That means we support finding a native library through the VM itself and 
through Classpath. For JamVM the latter one is used.