move wallet code to separate file

This introduces two new source files, keystore.cpp and wallet.cpp with
corresponding headers. Code is moved from main and db, in a preparation
for a follow-up commit which introduces the classes CWallet and CKeyStore.

src/makefile.mingw

@@ -33,7 +33,7 @@ DEFS=-DWIN32 -D__WXMSW__ -D_WINDOWS -DNOPCH -DUSE_SSL
 DEBUGFLAGS=-g -D__WXDEBUG__
 CFLAGS=-mthreads -O2 -w -Wno-invalid-offsetof -Wformat $(DEBUGFLAGS) $(DEFS) $(INCLUDEPATHS)
 HEADERS=headers.h strlcpy.h serialize.h uint256.h util.h key.h bignum.h base58.h \
-    script.h db.h net.h irc.h main.h rpc.h uibase.h ui.h noui.h init.h
+    script.h db.h net.h irc.h keystore.h main.h wallet.h rpc.h uibase.h ui.h noui.h init.h
 
 ifdef USE_UPNP
  INCLUDEPATHS += -I"C:\upnpc-exe-win32-20110215"
@@ -50,7 +50,9 @@ OBJS= \
     obj/db.o \
     obj/net.o \
     obj/irc.o \
+    obj/keystore.o \
     obj/main.o \
+    obj/wallet.o \
     obj/rpc.o \
     obj/init.o \
     cryptopp/obj/sha.o \