relax SVN archive

svn+ssh://bugman@.../svn/relax/trunk

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r18108 | bugman | 2012-12-11 15:47:47 +0100 (Tue, 11 Dec 2012) | 5 lines

Spun out code from generic_fns.pipes.create() into the new check_type() function.

This code will be reused in a new pipe user function.
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r18109 | bugman | 2012-12-11 15:58:13 +0100 (Tue, 11 Dec 2012) | 3 lines

Created the Pipes.test_change_type system test to check the non-existent pipe.change_type user function.
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r18110 | bugman | 2012-12-11 16:08:14 +0100 (Tue, 11 Dec 2012) | 3 lines

Implemented the pipe.change_type user function front and back ends.
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