applypatch changes for patching recovery image

Make some changes needed to applypatch in order to store the recovery
image in the system partition as a binary patch relative to the boot
image:

  - make applypatch use shared libraries, so it's smaller.  It will
    need to be on the main system so it can install the recovery
    image.  Make an applypatch_static binary for use in recovery
    packages (still needed for updating cupcake devices to donut).

  - output the results of patching to an in-memory buffer and write
    that to the partition; there's no convenient /tmp for us to us.
    (This should be basically a no-op in recovery, since /tmp is a
    ramdisk anyway.)

tools/applypatch/bsdiff.c

@@ -84,7 +84,7 @@ static off_t offtin(u_char *buf)
 
 int ApplyBSDiffPatch(const unsigned char* old_data, ssize_t old_size,
                      const char* patch_filename, ssize_t patch_offset,
-                     FILE* output, SHA_CTX* ctx) {
+                     SinkFn sink, void* token, SHA_CTX* ctx) {
 
   unsigned char* new_data;
   ssize_t new_size;
@@ -93,7 +93,7 @@ int ApplyBSDiffPatch(const unsigned char* old_data, ssize_t old_size,
     return -1;
   }
 
-  if (fwrite(new_data, 1, new_size, output) < new_size) {
+  if (sink(new_data, new_size, token) < new_size) {
     fprintf(stderr, "short write of output: %d (%s)\n", errno, strerror(errno));
     return 1;
   }