RFR(s): 8067631: hgforest.sh mishandles arguments with spaces

[Stuart Marks]

Hi all,

Please review this change to hgforest.sh, to preserve argument quoting when 
passing arguments with spaces through to the hg command.

Changeset (in the new sandbox repo):

     http://hg.openjdk.java.net/jdk9/sandbox/rev/886037762070

Bug:

     https://bugs.openjdk.java.net/browse/JDK-8067631

Thanks,

s'marks