RFR: 8279315: Add Git support to update_copyright_year.sh script [v2]

[Dmitry Kulikov]

> Modified the `make/scripts/update_copyright_year.sh` script to support Git as well as Mercurial, as per [JDK-8279315](https://bugs.openjdk.java.net/browse/JDK-8279315). Also added the ability to specify company name as a command line argument instead of being hard-coded into the script.

Dmitry Kulikov has updated the pull request incrementally with one additional commit since the last revision:

  Add VCS auto-detection

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7027/files
  - new: https://git.openjdk.java.net/jdk/pull/7027/files/17805219..670b50b2

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7027&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7027&range=00-01

  Stats: 24 lines in 1 file changed: 23 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7027.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7027/head:pull/7027

PR: https://git.openjdk.java.net/jdk/pull/7027