Suppress an error at bootstrap

"type glibtoolize" will display an error message if glibtoolize is not
found (on non-Mac OS X systems):
./bootstrap: line 12: type: glibtoolize: not found

"which glibtoolize" will be quiet. So we use it instead.

bootstrap

@@ -9,7 +9,7 @@ LIBTOOLIZE=libtoolize
 # ==> Caveats
 # In order to prevent conflicts with Apple's own libtool we have prepended a "g"
 # so, you have instead: glibtool and glibtoolize.
-type glibtoolize && LIBTOOLIZE=glibtoolize
+which glibtoolize && LIBTOOLIZE=glibtoolize
 
 aclocal -I m4
 $LIBTOOLIZE --copy --force --automake