Added Geoff's patch that allows defining the same struct in multiple .zir files and then linked into a single executable, using preprocessor directives
Added external DEFINES to preprocess compile of Ziria code in all scripts
Added external DEFINES to preprocess compile of Ziria code in all scripts (forgotten files)
Modified I/O function signatures and call points to add support for streams of structs
Added boilerplate for chunk buffers
Finished buf_chunk feature and added tests
Merge commit 'aaf88a472a9c40d80d5d88426b4d09' into dev

Conflicts:
	src/BasicTypes/AstExpr.hs
	src/Codegen/CgOpt.hs
	src/Codegen/CgRuntime.hs