RFR: Add tabfiles to jcheck configuration [v4]

[Magnus Ihse Bursie]

> The tabfiles setting is just like the files setting, but it lists files in which tabs are allowed.
> 
> (This is to support makefiles)

Magnus Ihse Bursie has updated the pull request incrementally with one additional commit since the last revision:

  Add tests of ignore-tabs jcheck functionality.

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Changes:
  - all: https://git.openjdk.java.net/skara/pull/929/files
  - new: https://git.openjdk.java.net/skara/pull/929/files/4aaa659f..0a196994

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=skara&pr=929&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=skara&pr=929&range=02-03

  Stats: 70 lines in 1 file changed: 62 ins; 2 del; 6 mod
  Patch: https://git.openjdk.java.net/skara/pull/929.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/929/head:pull/929

PR: https://git.openjdk.java.net/skara/pull/929