BUILD: fix dependencies between config and compat.h

compat.h only depends on the system, and config needs compat, not the
opposite. global.h was fixed to explicitly include standard.h for LONGBITS.
diff --git a/include/common/config.h b/include/common/config.h
index 5833cfc..27b8f14 100644
--- a/include/common/config.h
+++ b/include/common/config.h
@@ -23,6 +23,7 @@
 #define _COMMON_CONFIG_H
 
 #include <common/compiler.h>
+#include <common/compat.h>
 #include <common/defaults.h>
 
 /* this reduces the number of calls to select() by choosing appropriate