xlsxparse.cc: Correct "max" -> "min" when reserving space for shared
strings.  This only means we now reserve a more appropriate amount
of space to start with.

git-svn-id: file:///home/xapian-svn/xapian/trunk@17061 6b2f1b92-a4f3-0310-943f-de3cbe41748b
Makefile.am: Fix to work in VPATH build.

git-svn-id: file:///home/xapian-svn/xapian/trunk@17062 6b2f1b92-a4f3-0310-943f-de3cbe41748b