RFR: 8253948: Memory leak in ImageFileReader

[Zhengyu Gu]

On Fri, 2 Oct 2020 20:47:16 GMT, Zhengyu Gu <zgu at openjdk.org> wrote:

> ImageFileReader allocates ImageModuleData in ImageFileReader::open(), but never free.
> 
> Also renamed module_data to _module_data to be consistent with other member variables.
> 
> Test:
> - [x] tier1 on Linux x86_64

ImageFileReader is also used in hotspot runtime

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PR: https://git.openjdk.java.net/jdk/pull/490