#12 reduce handler memory usage

[Jeffrey L. Taylor]

expandContent, textContent, parseElementsInContent, and
parseEntitiesInContent are class static in value, i.e.,
all handlers of the same class have the same values and
they do not change over the lifetime of the object.
The access functions can be made virtual and then they
don't take up space in the member data. Alternatively,
they can be made bits instead of bool.

[Jeffrey L. Taylor]

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If bool type is reduced to less than int width, the virtual
function tables get compile warnings about initialization
from an incompatible pointer type (char and short don't
behave). This is true on both the SuSE 7.1 Linux and the
FreeBSD platforms, both with the gcc 2.95.2 compiler, and
Slackware 4.0 with the 2.7.2 compiler.