This makes sure that we catch all leftover instances of using SYB to do generic operations that we should be using Polyplate for instead. Most modules should only import Data, and possibly Typeable.
This fixes the problem with PROCs complaining that one munged version of the record name was not the same as another.
This will cause problems if two different record definitions for the same name are visible in the same file.
I'm not sure if this is a valid thing to do, but it solved a problem with the occam libraries where multiple occam files were including an inline FUNCTION from an include file, and this was causing problems at link time.
For some reason, the usage check tests are now very slow to run (perhaps because of all the operator definitions added to each one?), which needs further investigation.
The previous method, using the C preprocessor was both nasty, and crazily resource-intensive. The new method stores stack size information in files that are read in and processed by the compiler when it comes time to link.
This may seem like an odd change, but it simplifies the logic a lot. I kept having problems with passes not operating on externals (e.g. functions-to-procs, adding array sizes, constant folding in array dimensions) and adding a special case every time to also process the externals was getting silly.
Putting the externals in the AST therefore made sense, but I didn't want to just add dummy bodies as this would cause them to throw up errors (e.g. in the type-checking for functions). So I turned the bodies into a Maybe type, and that has worked out well.
I also stopped storing the formals in csExternals (since they are now in csNames, and the tree), which streamlined that nicely, and stopped me having to keep them up to date.
Now that we support separate compilation, some of the stack sizes for PROCs depend on the stack sizes of other PROCs that were compiled in different files. We can't just assume the default 512 bytes for these "foreign" PROCs, because that often won't be enough. So instead, we must make the stack sizes for the current PROCs depend on (i.e. use in the calculation) the stack sizes of the foreign PROCs.
This dependence adds some issues though. We cannot declare in one C file a const int that depends on the value of an extern const int from another C file (not valid C, it seems). So instead, we move all the stack size declarations to header files, and use #includes and the preprocessor to make sure that the stack sizes are statically determined.
This in turn simplifies the build process in some ways. These headers only need to be compiled by the .occ file that has the main process, by including them all into a C file and compiling that as before. It means that each .occ file only has one .o file resulting (plus two C headers*, and a .inc file) so linking is a bit less confusing.
* I am keeping the two C headers for now, rather than appending the sizes one to the normal header, because I'm not entirely sure whether having one header that the C file depends on may trigger a recompilation that we don't want in some build systems. I can always merge them later if that's not a valid worry.
This just about works, but it allocates the usual 512 bytes for all external PROCs being called, rather than using the actual stack_size for those external PROCs (this causes popcorn to overflow the stack if left with the default 512 bytes)
