solaris: tests can't use tail -n Solaris tail doesn't recognize the -n option. Replace the one use of it with some inline python code, and add a test case to check-code.py.

solaris: sed doesn't recognize a line without a newline

solaris: test cases can't use grep -a The -a option to GNU grep isn't available when using Solaris grep. Replace the one use of grep -a in the testsuite with some in-line Python that does the equivalent, and add a check for grep -a in check-code.py.

revlog: pass node as an argument of addrevision This change will allow revlog subclasses that override 'checkhash' method to use custom strategy of computing nodeids without overriding 'addrevision' method. In particular this change is necessary to implement manifest compression.

revlog: extract 'checkhash' method Extract method that decides whether nodeid is correct for paricular revision text and parent nodes. Having this method extracted will allow revlog subclasses to implement custom way of computing nodes. In particular this change is necessary to implement manifest compression.

histedit: discard meaningless comment about 'hexlify node' Refactoring in 26b41a902195 made this comment meaningless. The node gotten by "discovery.findcommonoutgoing()" is hexlified in "between()" by "repo.set('%n::%n', old, new)".