Quote regexes in test headers

[Lytigas]

When using test-one.sh, unquoted wildcards are expanded by the shell,
resulting in failing tests.

The issue showed itself via output similar to this:

$ ./test-one.sh constify-enum
warning: ..: 'linker' input unused [-Wunused-command-line-argument], err: false
warning: .git: 'linker' input unused [-Wunused-command-line-argument], err: false
warning: .gitattributes: 'linker' input unused [-Wunused-command-line-argument], err: false
warning: .github: 'linker' input unused [-Wunused-command-line-argument], err: false
warning: .gitignore: 'linker' input unused [-Wunused-command-line-argument], err: false
warning: .travis.yml: 'linker' input unused [-Wunused-command-line-argument], err: false
warning: .vscode: 'linker' input unused [-Wunused-command-line-argument], err: false
(
 kind = EnumDecl
 spelling = "nsCSSPropertyID"
...

which no longer shows after this patch.

[emilio]

Thanks!