analyzer: modules support

[griwes]

Significant changes:

• CMake instead of Make as the build system.
• Also build protobuf that's used for module interface files.

[griwes]

Short list of ideas and TODOs I've just thought of:

• [x] vprc must start invoking llc by itself, because otherwise compiling modules will be a total mess, and I can totally do it as part of modules.
  • [x] Use llvm-config to find where llc is and invoke that.
  • [x] Add an option to vprc to override which llvm-config to ask for --bindir.
• [x] -o isn't that great with modules. Should probably implement the entire set of GHC inspired flags: -o, -m for the interface file, -l (not sure if this is a good name) for llvm files, and then -odir to change directory for default -o, -mdir for default -m, and -ldir for default -l, and then finally -outdir for all of them. (Possibly make all of them double dashed?) And, well... Default output files.
• [x] The protocol for modules should include the compilation date, hash of the source file and the modification date of the source file. The import operations should verify all these against the possibly existing source file when a compiled module is found, to recompile it if necessary.
• [x] -mdir should obviously be in the module search path, but the question is: should it be on the top of the list? Probably should.

[griwes]

Additional one:

• [ ] configurable suffixes for the default output filenames, just like GHC does, might be a good idea, but I don't think it is necessary to implement them right now.