Avoid zlib symbol conflicts in open-vcdiff

sdch/sdch.gyp

Index: sdch/sdch.gyp
diff --git a/sdch/sdch.gyp b/sdch/sdch.gyp
index 410629f29004cfda613cc72fa646023a20d121a0..bb62bce8e3bf069d74af2cab5c3b255bef93ceb9 100644
--- a/sdch/sdch.gyp
+++ b/sdch/sdch.gyp
@@ -47,6 +47,11 @@
       'include_dirs': [
         'open-vcdiff/src',
       ],
+      'defines': [
+        # Prefix the local zlib function names (e.g. adler32 -> z_adler32) to
+        # avoid link warning due to name conflict with zlib.
+        'Z_PREFIX',

[tonyg, 2012/03/01 11:32:54]

Sorry for the naive question, but why is there a local zlib in the first place.
If it is unmodified can we remove it? If it is heavily modified, should it just
be renamed so as to not conflict in the first place?

[Xianzhu, 2012/03/01 17:44:44]

Good question. I just compared sdch/open-vcdiff/src/adler32.c and
third_party/zlib/adler32.c and I believe the differences won't have any effect.
I'll try to let sdch depend on zlib.

+      ],
       'direct_dependent_settings': {
         'include_dirs': [
           'open-vcdiff/src',