Run textwrap.dedent on text files created by the test runner

[sbc100]

This means we can indent out test snippets in the python code and should never need to use column 1.

The files on disc that the test runner writes will have sane/normal indentation even if we use extra indentation in the python source to make things readable.

For example:

    create_file('a.c', '''
       int main()
         printf("hello\n");
       }
    ''')

Would generate a file on disc containing:

int main()
  printf("hello\n");
}

[kripken]

lgtm if tests pass. I worry some test might care about the indentation... but maybe we already dedented those manually before.

[sbc100]

lgtm if tests pass. I worry some test might care about the indentation... but maybe we already dedented those manually before.

Its possible, but very unlikely, and we would know right away if a test was effected by this. Most significant tests already use standalone files rather then embedding sources.