[stdlib] Math.mul_div bugfix

[xfhxfh1212]

fix wrong caculation

[jolestar]

@xfhxfh1212 thanks!

修改后需要在 vm/stdlib 和 genesis 目录下运行 cargo run，编译 stdlib 和生成 genesis， 然后把生成的文件也提交上来。

[codecov]

Codecov Report

Merging #2775 (e3b23c3) into master (913cc81) will increase coverage by 0.24%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2775      +/-   ##
==========================================
+ Coverage   31.58%   31.81%   +0.24%     
==========================================
  Files         508      508              
  Lines       44778    44778              
  Branches    19929    19929              
==========================================
+ Hits        14139    14242     +103     
+ Misses      16991    16751     -240     
- Partials    13648    13785     +137     

Flag	Coverage Δ
unittests	31.81% <ø> (+0.24%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
commons/timeout-join-handler/src/lib.rs	40.43% <0.00%> (-4.25%)	⬇️
node/src/lib.rs	18.75% <0.00%> (ø)
types/src/peer_info.rs	51.56% <0.00%> (ø)
network/api/src/tests.rs	22.06% <0.00%> (ø)
network-p2p/src/protocol.rs	41.26% <0.00%> (ø)
network-p2p/types/src/lib.rs	34.41% <0.00%> (ø)
miner/src/create_block_template/mod.rs	42.39% <0.00%> (ø)
vm/vm-runtime/src/starcoin_vm.rs	29.29% <0.00%> (+0.14%)	⬆️
...able-jellyfish-merkle/src/jellyfish_merkle_test.rs	19.07% <0.00%> (+0.23%)	⬆️
...etwork-p2p/src/protocol/generic_proto/behaviour.rs	20.74% <0.00%> (+0.27%)	⬆️
... and 19 more

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