database: pull out database code into a new module

We're going to reuse the database controllers for the accounting plugin

.gitattributes

@@ -7,8 +7,8 @@ configure text eol=lf
 # The following files are generated and should not be shown in the
 # diffs by default on Github.
 doc/lightning*.7 linguist-generated=true
-wallet/db_*_sqlgen.c linguist-generated=true
-wallet/statements_gettextgen.po linguist-generated=true
+db_*_sqlgen.c linguist-generated=true
+statements_gettextgen.po linguist-generated=true
 *_wiregen.? linguist-generated=true
 *_printgen.? linguist-generated=true
 

Makefile

@@ -336,6 +336,7 @@ include external/Makefile
 include bitcoin/Makefile
 include common/Makefile
 include wire/Makefile
+include db/Makefile
 include hsmd/Makefile
 include gossipd/Makefile
 include openingd/Makefile

db/Makefile

@@ -0,0 +1,23 @@
+#! /usr/bin/make
+
+DB_LIB_SRC := 			\
+	db/bindings.c		\
+	db/exec.c		\
+	db/utils.c
+
+DB_DRIVERS :=			\
+	db/db_postgres.c	\
+	db/db_sqlite3.c
+
+DB_SRC := $(DB_LIB_SRC) $(DB_DRIVERS)
+DB_HEADERS := $(DB_LIB_SRC:.c=.h) db/common.h
+
+DB_OBJS := $(DB_LIB_SRC:.c=.o) $(DB_DRIVERS:.c=.o)
+$(DB_OBJS): $(DB_HEADERS)
+
+# Make sure these depend on everything.
+ALL_C_SOURCES += $(DB_SRC)
+ALL_C_HEADERS += $(DB_HEADERS)
+
+# DB_SQL_FILES is the list of database files
+DB_SQL_FILES := db/exec.c