db_mysql: fixing include in Makefile for many paths

- sed matching should break at whitespace, to fix the case when
  mysql_config returns multiple include paths
- reported by FS#503

modules/db_mysql/Makefile

@@ -21,7 +21,7 @@ endif
 
 ifneq ($(MYSQLCFG),)
 	# use autodetection
-	DEFS += $(shell $(MYSQLCFG) --include | sed 's/\(-I.*\)\/mysql/\1/g' )
+	DEFS += $(shell $(MYSQLCFG) --include | sed 's/\(-I[^ ]*\)\/mysql/\1/g' )
 	LIBS = $(shell $(MYSQLCFG) --libs)
 else
 	# mysql.h locations (freebsd,openbsd  solaris)