Bug #5492 
"set @@session.read_rnd_buffer_size=33554432" crashes server on query

1. added warning comments for uint3korr (need one more byte allocated)
2. unsigned long in uint3korr was replaced by unsigned int to 
   avoid problems on 64-bits platforms
3. shorten warning comments in init_rr_cache in sql/records.cc


include/config-win.h:
  1. added warning comments for uint3korr (need one more byte allocated)
  2. unsigned long in uint3korr was replaced by unsigned int to 
     avoid problems on 64-bits platforms
include/my_global.h:
  1. added warning comments for uint3korr (need one more byte allocated)
  2. unsigned long in uint3korr was replaced by unsigned int to 
     avoid problems on 64-bits platforms
sql/records.cc:
  shorten warning comments for my_malloc_lock in init_rr_cache