Fix assorted issues with build and install paths containing spaces.

Apparently there is no buildfarm critter exercising this case after all,
because it fails in several places.  With this patch, build, install,
check-world, and installcheck-world pass for me on OS X.

config/mkinstalldirs

@@ -105,13 +105,15 @@ esac
 
 for file
 do
-  set fnord `echo ":$file" | sed -ne 's/^:\//#/;s/^://;s/\// /g;s/^#/\//;p'`
+  # pathcomp starts with leading slash if present, else empty
+  pathcomp=`echo "$file" | sed -ne 's|^\(.\).*$|\1|;s|[^/]||;p'`
+  # swap spaces and slashes, then split on spaces
+  set fnord `echo "$file" | tr ' /' '/ '`
   shift
 
-  pathcomp=
   for d
   do
-    pathcomp="$pathcomp$d"
+    pathcomp="$pathcomp"`echo "$d" | tr '/' ' '`
     case $pathcomp in
       -*) pathcomp=./$pathcomp ;;
     esac