Prevent writing out empty style strings.

cppcheck

cppcheck: style and performance

Don't remove default css values if element is in <defs> or is a <symbol>.

some memleak fixes (Bug #1043571)

revert rev 11646: build issue with dbus (forgot to adapt some more, dbus was not enabled) and other issues

converted some c-string usage to c++ string class usage: should fix some memory leaks

Janitorial tasks: get rid of deprecated repr wrapper functions

Add feMergeNode to "in" list in svgprops. Fix bug in preferences for deleting invalid attributes.

Add possibility to check validity of attributes and usefulness of properties. This code adds the ability to check for every elment in an SVG document if its attributes are valid and the styling properties are useful. Options under the SVG Output section of the Inkscape Preferences dialog control what should be checked when, and what actions should be taken if invalid attributes or non-useful properties are found.