docker/docker — pull request #8370 by duglin (2014-10-03 00:06:49+00:00)
Title: Fix builder/parser so it keeps some whitespace on split lines.

If previous line ends with whitespace, or next line starts with whitepsace
we need to preserve a space otherwise things line:
RUN echo\
hello
will appear as: RUN echohello

Noticed this while looking at #5744 because he had lines ending in &&\

Signed-off-by: Doug Davis