build errors on Yosemite version of clang

[larkost]

There was a post-Yosemite upgrade of Xcode that carried with it a new version of clang, and it seems it finds new problems in our codebase:

In file included from src/rdb_protocol/geo/indexing.cc:18:
In file included from ./src/rdb_protocol/geo/s2/strings/strutil.h:44:
./src/rdb_protocol/geo/s2/util/endian/endian.h:175:9: error: 'htonll' macro redefined [-Werror]
#define htonll(x) ghtonll(x)
        ^
/usr/include/sys/_endian.h:141:9: note: previous definition is here
#define htonll(x)       __DARWIN_OSSwapInt64(x)
        ^
In file included from src/rdb_protocol/geo/indexing.cc:18:
In file included from ./src/rdb_protocol/geo/s2/strings/strutil.h:44:
./src/rdb_protocol/geo/s2/util/endian/endian.h:182:9: error: 'ntohll' macro redefined [-Werror]
#define ntohll(x) htonll(x)
        ^
/usr/include/sys/_endian.h:140:9: note: previous definition is here
#define ntohll(x)       __DARWIN_OSSwapInt64(x)
        ^

I am unable to build next on my local machine, but gantz (Mavericks) is building the same version fine. For reference the versions of clang:

Mavericks: Apple LLVM version 6.0 (clang-600.0.51) (based on LLVM 3.5svn)
Yosemite: Apple LLVM version 6.0 (clang-600.0.54) (based on LLVM 3.5svn)

(yes... new build of the same "version")

[AtnNn]

The problem seems to be that the system include files (specifically /usr/include/sys/_endian.h) now define those two macros while previous versions didn't.

Those macros are defined in the s2 code, but don't seem to be used anywhere. We could wrap them in an #ifdef or just remove them.

[danielmewes]

(So far I've usually removed platform-specific parts of S2 that were not used.)

[larkost]

I fixed this by putting in ifdefs around the two problematic declarations. That appears to solve the problem. It is in next with ea2c2d7, and was over-the-shouldered by @danielmewes