[PATCH] Trim leading and trailing spaces after OGR_F_GetFieldAsString

[rouault]

OGR_F_GetFieldAsString() may return leading spaces on a numeric field which has a non-zero width. This behaviour is wanted in OGR, but not in the results returned by mapserver (WFS request, etc..)

Note: this patch could be made more specific to only deal with numeric fields, in situations where string fields should be preserved without change