fix memory management bookkeeping issue

[zhanghongce]

Purpose

fix memory management accounting issue

List of changes

• verilog_ast_mem.c: counting the size using the correct block size.
• verilog_ast_mem.c: deduct the freed bytes from total_allocated when freed. So the bookkeeping is reusable.

[coveralls]

Coverage increased (+0.007%) to 66.608% when pulling d860f41 on zhanghongce:mainstream into f7463ca on ben-marshall:master.

[ben-marshall]

Thank you kindly! 👍

[zhanghongce]

You are very welcome! There seems to be another issue in the preprocessor. But it is not very obvious what should be the correct fix for that. I think I may need to discuss with you later about what you were thinking about when you wrote that part, so as not to create a fix that changes what you meant. Will update you later.

Happy Holidays!:santa::christmas_tree: