scm: use shell quote for scm command at adapter level (#7517, #4273).
"C:\Program Files\TortoiseHg\hg.exe" can be used in config/configuration.yml.
In Ruby 1.9 IO.popen, if cmd is an Array of String, it will be used as the subprocess‘s argv bypassing a shell.
See http://www.ruby-doc.org/core/classes/IO.html
Authored by: tmaruyama 2011-02-14
Parent: [r4820]
Child: [r4822]