Compile fanvanzh's 3dtiles in Linux

Working for fanvanzh's 3dtiles Linux compilation for days. Some items for reminding everybody how wants to do the same thing.

liwei0705 did a good move in making fanvanzh's 3dtiles converter works. But if you are using a new version of OSG and GDAL, pay attention to the following summarised reminders when building your own version of "_3dtile"

• Delete 3dtiles/bin, it is for windows only

• Compile your own OpenSceneGraph
• Copy OpenSceneGraph /lib to 3dtiles
• Copy OpenSceneGraph /include/* to 3dtiles/src/osg/*

• If not compile OpenSceneGraph on your own, you can install "openscenegraph" and "libopenscenegraph-dev" instead
• Delete /lib in 3dtiles (the /lib is for self-compiled OSG, GDAL actually)
• Delete 3dtiles/src/osg/ (no need to provide OSG header, use the one in libopenscenegraphi-dev)

• Install gdal-bin, libgdal-dev
• rm -rf 3dtiles/src/gdal (we will use libraries and header by gdal-bin and libgdal-dev)

• Source file: src/tileset.cpp
• Hide up #ifdef _WIN32, turn on "epsg_convert" and "wkt_convert"
• Comment out GDAL_DATA: 
• // CPLSetConfigOption("GDAL_DATA", path);

• For epsg_convert( )
• Don't use importFromEPSG(), use:
• // For 2326 Input (Hard code the input SRS) (Ref)
• inRs.importFromProj4("+proj=tmerc +lat_0=22.3121333333333 +lon_0=114.178555555556 +k=1 +x_0=836694.05 +y_0=819069.8 +ellps=intl +towgs84=-162.619,-276.959,-161.764,-0.067753,2.243648,1.158828,-1.094246 +units=m +no_defs +type=crs");
• // for 4326 Output (Hard code the output SRS) (Ref)
• outRs.importFromProj4("+proj=longlat +datum=WGS84 +no_defs +type=crs");

• Source file: src/earcut.hpp
• Add header files
• #include <stdexcept>
• #include <limits>

• Source file: build.rs
• In linux bulid config, add:
• println!("cargo:rustc-link-lib=gdal");

• When running the ./target/release/_3dtile
• export LD_LIBRARY_PATH=./lib

• Side notes, if you use "cargo run" for debugging and when to rebuild the project when some CPP files are modified, add the following in linux build config (build.rs): (reference)
• println!("cargo:rerun-if-changed=./src/tileset.cpp");