Small fix of column number in parser

[Daniel Kraft]

Hi all,

attached is a hg changeset that fixes wrong column numbers.  If the 
attached test.m is executed without the patch, one gets:

error: bar
error: called from:
error:   /tmp/test.m at line 2, column -1

With the patch, the column number is correctly reported as 1.

Note that this is somewhat the "minimal" version of the fix; since 
skip_white_space is only used once (in gobble_white_space) and also the 
stdio_stream_reader class is only used there, it may be nice to somewhat 
unify the code.  Currently, line-numbers are tracked in 
stdio_stream_reader and column-numbers in skip_white_space.

Do you prefer this simple patch or should I work on some "clean-up" of 
this situation, too -- like making skip_white_space a member of 
stdio_stream_reader and unifying column- and line-number tracking in one 
place.

Yours,
Daniel

PS: Since this is my first attempt at both working with Mercurial and 
submitting a patch for octave, please let me know if there's something I 
should do different (and in general, comments welcome).  In particular, 
is there some tag I should add to messages sent with patches?  E.g., on 
the GCC lists, we have "[patch]" in the subjects of messages containing 
diff's.

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test.m
Description: Text document

column.diff
Description: Text document