Add berkelydb version warning

README.rst

@@ -60,3 +60,18 @@ Alternatively, install Qt Creator and open the `bitcoin-qt.pro` file.
 
 An executable named `bitcoin-qt` will be built.
 
+Berkely DB version warning
+==========================
+
+A warning for people using the *static binary* version of Bitcoin (tl;dr: **Berkely DB databases are not forward compatible**).
+
+The static binary version of Bitcoin is linked against libdb4.7 or libdb4.8 (see also `this Debian issue`_).
+
+Now the nasty thing is that databases from 5.X are not compatible with 4.X. 
+
+If the globally installed development package of Berkely DB installed on your system is 5.X, any source you
+build yourself will be linked against that. The first time you run with a 5.X version the database will be upgraded, 
+and 4.X cannot open the new format. This means that you cannot go back to the old statically linked version without
+significant hassle!
+
+.. _`this Debian issue`: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=621425

bitcoin-qt.pro

@@ -2,13 +2,15 @@ TEMPLATE = app
 TARGET =
 DEPENDPATH += .
 INCLUDEPATH += src src/json src/cryptopp src/qt
+
+# for boost 1.37, add -mt to the boost libraries
 unix:LIBS += -lssl -lcrypto -lboost_system -lboost_filesystem -lboost_program_options -lboost_thread -ldb_cxx
 macx:DEFINES += __WXMAC_OSX__ MSG_NOSIGNAL=0
 
-# disable quite some warnings becuase bitcoin core "sins" a lot
+# disable quite some warnings because bitcoin core "sins" a lot
 QMAKE_CXXFLAGS_WARN_ON = -fdiagnostics-show-option -Wall -Wno-invalid-offsetof -Wno-unused-variable -Wno-unused-parameter -Wno-sign-compare -Wno-char-subscripts  -Wno-unused-value -Wno-sequence-point -Wno-parentheses -Wno-unknown-pragmas -Wno-switch
 
-# WINDOWS defines, -DSSL, look at build system
+# TODO: WINDOWS defines, -DSSL
 
 # Input
 DEPENDPATH += src/qt src src/cryptopp src json/include