When using bundled zlib, INNODB_PLUGIN was looking for

zlib headers in wrong location.

Fixed by using path exported by zlib.m4 macro.

storage/innodb_plugin/Makefile.am:
  Include zlib headers from a proper location.

storage/innodb_plugin/Makefile.am

@@ -24,7 +24,7 @@ INCLUDES=		-I$(top_srcdir)/include -I$(top_builddir)/include \
 			-I$(top_srcdir)/regex \
 			-I$(srcdir)/include \
 			-I$(top_srcdir)/sql \
-			-I$(srcdir)
+			-I$(srcdir) @ZLIB_INCLUDES@
 
 DEFS=			@DEFS@