[clang-tidy] Add new 'readability-uppercase-literal-suffix' check (CERT...

[clang-tidy] Add new 'readability-uppercase-literal-suffix' check (CERT DCL16-C, MISRA C:2012, 7.3, MISRA C++:2008, 2-13-4)

Summary:
Detects when the integral literal or floating point (decimal or hexadecimal)
literal has non-uppercase suffix, and suggests to make the suffix uppercase,
with fix-it.

All valid combinations of suffixes are supported.

```
  auto x = 1;  // OK, no suffix.

  auto x = 1u; // warning: integer literal suffix 'u' is not upper-case

  auto x = 1U; // OK, suffix is uppercase.

  ...
```

References:
* [[ https://wiki.sei.cmu.edu/confluence/pages/viewpage.action?pageId=87152241 | CERT DCL16-C ]]
* MISRA C:2012, 7.3 - The lowercase character "l" shall not be used in a literal suffix
* MISRA C++:2008, 2-13-4 - Literal suffixes shall be upper case

Reviewers: JonasToth, aaron.ballman, alexfh, hokein, xazax.hun

Reviewed By: aaron.ballman

Subscribers: Eugene.Zelenko, mgorny, rnkovacs, cfe-commits

Tags: #clang-tools-extra

Differential Revision: https://reviews.llvm.org/D52670

llvm-svn: 344755