[clang-tidy] Fix bugprone-argument-comment bug: negative literal number is not checked.

Summary:
For example:
```
void foo(int a);
foo(-2);
```
should be fixed as:
```
foo(/*a=*/-2);
```
This change tries to fix this issue.

Reviewers: alexfh, hokein, aaron.ballman

Reviewed By: alexfh, aaron.ballman

Subscribers: xazax.hun, cfe-commits

Tags: #clang, #clang-tools-extra

Patch by Yubo Xie.

Differential Revision: https://reviews.llvm.org/D67084

llvm-svn: 371072