Fix: String variable with whitespaces were incorrectly parsed.

The strings were only parsed until the first whitespace was encountered. Note that leading and trailing whitespaces are removed by design.

Also backport that fix to XIOS 1.0.

This commit fixes ticket #60.

git-svn-id: http://forge.ipsl.jussieu.fr/ioserver/svn/XIOS/branchs/xios-1.0@530 d613d254-d18a-4304-b296-5125d4c4d670