... and fix the wrong export for <text:meta-field>, which erroneously
did not use the same bIsPrevCharSpace flag as everything else (which was
obviously a bug, as there should be one flag per paragraph).

Interop testing demonstrates that at least Word and Calligra Words
differ in their interpretation of spaces following <draw:frame> and
other shape elements, and <text:note>: if there is a U+0020 space
before the element, LO will not collapse a U+0020 space behind the
element but Word and Calligra Words do collapse it.

The distinction between "mark elements" and "non-mark elements" in the
whitespace collapsing implementation in OOo since the beginning was
never explicitly spelled out in ODF, although listing the
<text:bookmark> etc. elements in ODF 1.1, 5.1.1 was a strong hint.

Fortunately all 3 applications agree that a <text:s> following a
<draw:frame> is consumed as a space, and it is valid to write a <text:s>
in this situation, so just do that to improve interoperability.

Change-Id: I42260c0528db9fe7e87e8dbae5105aeadb83780d