Add HTTP protocol using curl v6

Currently Qemu can read from posix I/O and NBD. This patch adds a
third protocol to the game: HTTP.

In certain situations it can be useful to access HTTP data directly,
for example if you want to try out an http provided OS image, but
don't know if you want to download it yet.

Using this patch you can now try it on on the fly. Just use it like:

qemu -cdrom http://host/path/my.iso

Signed-off-by: Alexander Graf <agraf@suse.de>
diff --git a/Makefile b/Makefile
index 49fd2fa..781e7ed 100644
--- a/Makefile
+++ b/Makefile
@@ -80,6 +80,10 @@
 BLOCK_OBJS += block/raw-posix.o
 endif
 
+ifdef CONFIG_CURL
+BLOCK_OBJS += block/curl.o
+endif
+
 ######################################################################
 # libqemu_common.a: Target independent part of system emulation. The
 # long term path is to suppress *all* target specific code in case of
@@ -196,6 +200,8 @@
   OBJS += $(XEN_OBJS)
 endif
 
+LIBS+=$(CURL_LIBS)
+
 cocoa.o: cocoa.m
 
 keymaps.o: keymaps.c keymaps.h