Fix build without zlib

Don't include unconditionally zlib.h, and compile out code that
requires zlib support.

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>

diff -durN mysql-5.1.73.orig/mysys/checksum.c mysql-5.1.73/mysys/checksum.c
--- mysql-5.1.73.orig/mysys/checksum.c	2020-07-14 17:34:38.212304432 +0200
+++ mysql-5.1.73/mysys/checksum.c	2020-07-14 18:06:45.076342493 +0200
@@ -16,7 +16,9 @@
 
 #include <my_global.h>
 #include <my_sys.h>
+#ifdef HAVE_COMPRESS
 #include <zlib.h>
+#endif
 
 /*
   Calculate a long checksum for a memoryblock.
diff -durN mysql-5.1.73.orig/sql/item_strfunc.cc mysql-5.1.73/sql/item_strfunc.cc
--- mysql-5.1.73.orig/sql/item_strfunc.cc	2020-07-14 17:34:38.160304431 +0200
+++ mysql-5.1.73/sql/item_strfunc.cc	2020-07-14 18:04:36.956339962 +0200
@@ -35,7 +35,9 @@
 #include "my_md5.h"
 #include "sha1.h"
 #include "my_aes.h"
+#ifdef HAVE_COMPRESS
 #include <zlib.h>
+#endif
 C_MODE_START
 #include "../mysys/my_static.h"			// For soundex_map
 C_MODE_END
diff -durN mysql-5.1.73.orig/sql/sql_table.cc mysql-5.1.73/sql/sql_table.cc
--- mysql-5.1.73.orig/sql/sql_table.cc	2020-07-14 17:34:38.156304431 +0200
+++ mysql-5.1.73/sql/sql_table.cc	2020-07-14 18:14:48.628352044 +0200
@@ -1681,6 +1681,7 @@
       goto end;
     }
   }
+#ifdef HAVE_COMPRESS
   if (flags & WFRM_PACK_FRM)
   {
     /*
@@ -1702,6 +1703,7 @@
     }
     error= my_delete(shadow_frm_name, MYF(MY_WME));
   }
+#endif
   if (flags & WFRM_INSTALL_SHADOW)
   {
 #ifdef WITH_PARTITION_STORAGE_ENGINE