Dynamic Linking

[shelhamer]

Link the tools, tests, examples and pycaffe dynamically, drop the static tests, and set rpath so everything works within the caffe dir. This should reduce the build size and prepares for the Python layer in #1703.

Thoughts:

• resolving LINKFLAGS, LDFLAGS, and DYNAMIC_LDFLAGS could be a good idea.
• is the origin rpath worth it? I suppose it is to make everything work out of the box.
• matcaffe is still static -- I don't know anything about mex linking and there isn't a MATLAB layer to motivate it (yet)

@longjon should surely check this.

[longjon]

@shelhamer I've updated this:

• DYNAMIC_LDFLAGS serves no purpose when rpath has to be set explicitly anyway, so get rid of it.
• Set rpath everywhere it's needed, so Travis passes now.
• Make DYNAMIC_NAME an order dependency.
• Add the appropriate incantations for OS X. This builds and "runs" for me, but make pytest crashes on my machine. I think this is a personal configuration problem, so you may wish to try with your own OS X setup.

[shelhamer]

Sweet -- this checks out for me on OS X and a linux machine. Thanks Jon!

[shelhamer]

Fixed rpath for examples in 5c81243.

[jeffdonahue]

Just wanted to say this is awesome, thanks for doing this @shelhamer & @longjon. Changing core code and doing an incremental build with make -j everything is now practically instant since the tests aren't rebuilt, and the build dir with both debug and release builds is <500 MB now (rather than ~2 GB).