[RS] Support RenderScript struct allocations

This patch adds functionality for dumping allocations of struct elements. This involves:

    + Jitting the runtime for details on all the struct fields.

    + Finding the name of the struct type by looking for a global variable of the same type, which will have been reflected back to the java host code.

    + Using this struct type name to pass into expression evaluation for pretty printing the data for the dump command.

llvm-svn: 254294