Let mansyntax.sh work regardless of where it is called from.

tests/mansyntax.sh

@@ -6,7 +6,7 @@ set -e
 # Run syntax checks for all manpages in the documentation tree.
 #
 
-srcdir=${srcdir:-$PWD}
+srcdir="`cd $(dirname $0);pwd`"
 mandir=${srcdir}/../docs
 
 #