xa: fix build on 10.9 and add test

Formula/xa.rb

@@ -5,10 +5,57 @@ class Xa < Formula
   url 'http://www.floodgap.com/retrotech/xa/dists/xa-2.3.5.tar.gz'
   sha1 'd8f4564953adfcee69faacfa300b954875fabe21'
 
+  def patches
+    # From upstream: http://www.floodgap.com/retrotech/xa/xa-getline-patch.txt
+    # Filenames have been changed in the header ("xa.c" -> "a/src/xa.c")
+    # because the original patch can't be applied with -p0 or -p1.
+    # This fix will be in 2.3.6
+    DATA
+  end
+
   def install
     system "make", "CC=#{ENV.cc}",
                    "CFLAGS=#{ENV.cflags}",
                    "DESTDIR=#{prefix}",
                    "install"
   end
+
+  test do
+    (testpath/"foo.a").write "jsr $ffd2\n"
+
+    system "#{bin}/xa", "foo.a"
+    code = File.open("a.o65", "rb") { |f| f.read.unpack("C*") }
+    assert_equal [0x20, 0xd2, 0xff], code
+  end
 end
+
+__END__
+--- a/src/xa.c	2014-02-07 13:50:18.000000000 -0800
++++ b/src/xa.c	2014-02-07 13:51:27.000000000 -0800
+@@ -87,7 +87,7 @@
+ static int puttmp(int);
+ static int puttmps(signed char *, int);
+ static void chrput(int);
+-static int getline(char *);
++static int xgetline(char *);
+ static void lineout(void);
+ static long ga_p1(void);
+ static long gm_p1(void);
+@@ -763,7 +763,7 @@
+ 	temp_er = 0;
+ 
+ /*FIXIT*/
+-     while(!(er=getline(s)))
++     while(!(er=xgetline(s)))
+      {         
+           er=t_p1((signed char*)s,o,&l,&al);
+ 	  switch(segment) {
+@@ -1002,7 +1002,7 @@
+ 
+ static char l[MAXLINE];
+ 
+-static int getline(char *s)
++static int xgetline(char *s)
+ {
+      static int ec;
+