Build with BerkeleyDB >= 4.6

Index: build-aux/m4/bitcoin_find_bdb48.m4
--- build-aux/m4/bitcoin_find_bdb48.m4.orig
+++ build-aux/m4/bitcoin_find_bdb48.m4
@@ -22,7 +22,7 @@ AC_DEFUN([BITCOIN_FIND_BDB48],[
       AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
         #include <${searchpath}db_cxx.h>
       ]],[[
-        #if !((DB_VERSION_MAJOR == 4 && DB_VERSION_MINOR >= 8) || DB_VERSION_MAJOR > 4)
+        #if !((DB_VERSION_MAJOR == 4 && DB_VERSION_MINOR >= 6) || DB_VERSION_MAJOR > 4)
           #error "failed to find bdb 4.8+"
         #endif
       ]])],[
@@ -35,7 +35,7 @@ AC_DEFUN([BITCOIN_FIND_BDB48],[
       AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
         #include <${searchpath}db_cxx.h>
       ]],[[
-        #if !(DB_VERSION_MAJOR == 4 && DB_VERSION_MINOR == 8)
+        #if !(DB_VERSION_MAJOR == 4 && DB_VERSION_MINOR == 6)
           #error "failed to find bdb 4.8"
         #endif
       ]])],[
