title: In clang-tidy, how to set a check option that accepts at list of numbers
body: <p>I am using clang-tidy with a <code>.clang-tidy</code> configuration file. The file is read correctly, and I am able to set any kind of check options, except for check options that take a list of numbers as a value.</p>
  
  <p>Here is my <code>.clang-tidy</code> file, which attempts to set the check options <code>modernize-use-nullptr.NullMacros</code> and <code>readability-magic-numbers.IgnoredIntegerValues</code>:</p>
  
  <pre><code>Checks: 'modernize-use-nullptr,readability-magic-numbers'
  CheckOptions:
    - key:             modernize-use-nullptr.NullMacros
      value:           IT_WORKS_WITH_A_SIMPLE_VALUE
    - key:             readability-magic-numbers.IgnoredIntegerValues
      value:           '5;6;7;8;'
  </code></pre>
  
  <p>When I run clang-tidy with the <code>--dump-config</code> option, I get the following result:</p>
  
  <pre><code>---
  Checks:          'clang-diagnostic-*,clang-analyzer-*,modernize-use-nullptr,readability-magic-numbers'
  WarningsAsErrors: ''
  HeaderFilterRegex: ''
  AnalyzeTemporaryDtors: false
  FormatStyle:     none
  User:            user
  CheckOptions:
    - key:             cert-dcl16-c.NewSuffixes
      value:           'L;LL;LU;LLU'
    - key:             cert-oop54-cpp.WarnOnlyIfThisHasSuspiciousField
      value:           '0'
    - key:             cppcoreguidelines-explicit-virtual-functions.IgnoreDestructors
      value:           '1'
    - key:             cppcoreguidelines-non-private-member-variables-in-classes.IgnoreClassesWithAllMemberVariablesBeingPublic
      value:           '1'
    - key:             google-readability-braces-around-statements.ShortStatementLines
      value:           '1'
    - key:             google-readability-function-size.StatementThreshold
      value:           '800'
    - key:             google-readability-namespace-comments.ShortNamespaceLines
      value:           '10'
    - key:             google-readability-namespace-comments.SpacesBeforeComments
      value:           '2'
    - key:             modernize-loop-convert.MaxCopySize
      value:           '16'
    - key:             modernize-loop-convert.MinConfidence
      value:           reasonable
    - key:             modernize-loop-convert.NamingStyle
      value:           CamelCase
    - key:             modernize-pass-by-value.IncludeStyle
      value:           llvm
    - key:             modernize-replace-auto-ptr.IncludeStyle
      value:           llvm
    - key:             modernize-use-nullptr.NullMacros
      value:           IT_WORKS_WITH_A_SIMPLE_VALUE
    - key:             readability-magic-numbers.IgnoredFloatingPointValues
      value:           '1.0;100.0;'
    - key:             readability-magic-numbers.IgnoredIntegerValues
      value:           '1;2;3;4;'
  ...
  </code></pre>
  
  <p>As you can see, the <code>modernize-use-nullptr.NullMacros</code>
   check option was set correctly, but the <code>readability-magic-numbers.IgnoredIntegerValues</code> check option wasn't set.</p>
  
  <p>I think it is probably a problem of syntax, but I use the same syntax as the one given by <code>--dump-config</code>, which is supposed to be the right syntax according to clang-tidy documentation.</p>
  
  <p>How can I set the <code>readability-magic-numbers.IgnoredIntegerValues</code> check option?</p>
  
  <p>Running <code>clang-tidy --version</code> gives the following result:</p>
  
  <pre><code>LLVM (http://llvm.org/):
    LLVM version 9.0.1
    Optimized build.
    Default target: x86_64-pc-linux-gnu
    Host CPU: ivybridge
  </code></pre>