Implement new handling for margin and line-width settings.

Implement new handling for margin and line-width settings.

Make default left- and right-margins accessible in paper-defaults-init.ly. Look whether line-width, left-margin and/or right-margin are set, calculate missing values and check if systems would run off the page. Set default values in such cases.

[joeneeman, 2009-08-12 04:06:52]

Could you add some regression tests (doesn't have to be in this commit) that
demonstrate some of the possible combinations of margin settings? There should
also be some tests that demonstrate the warnings.

http://codereview.appspot.com/104085/diff/1/4
File lily/output-def.cc (right):

http://codereview.appspot.com/104085/diff/1/4#newcode149
Line 149: if ((lookup_variable (ly_symbol2scm ("is-layout")) == SCM_BOOL_T) &&
(scm_line_width != SCM_UNDEFINED)) return;
put the return on a separate line

http://codereview.appspot.com/104085/diff/1/4#newcode183
Line 183: if (paper_width != (line_width + left_margin + right_margin))
In case there is rounding, it is better to check
if (abs (paper_width - line_width - left_margin - right_margin) > 1e-6)

http://codereview.appspot.com/104085/diff/1/4#newcode205
Line 205: scm_from_double(paper_width - left_margin_default -
right_margin_default));
indentation