Add install target in Makefile

Add install target in Makefile

diff --git a/Makefile b/Makefile
index 700c821..cf8a967 100644
--- a/Makefile
+++ b/Makefile
@@ -1,5 +1,7 @@
-CFLAGS := -g -Wall
-LDFLAGS += -lpthread
+PREFIX    = /usr/local
+CFLAGS    := -g -Wall
+LDFLAGS   += -lpthread
+DESTDIR   =
 
 OBJ := aer-inject.o util.o aer.tab.o lex.yy.o
 GENSRC := aer.tab.c aer.tab.h lex.yy.c
@@ -31,4 +33,8 @@
 
 Makefile: .depend
 
+install: aer-inject
+       install -d $(DESTDIR)$(PREFIX)
+       install aer-inject $(DESTDIR)$(PREFIX)
+
 include .depend