Toying with a direct C "includes" in the compiler

[elcritch]

I'm avoiding doing useful things at the moment. So I tweaked the source filters 
in the compiler to include raw C files.

Here's an example:
    
    
    import hashes
    include "testing.c"
    
    proc add(a, b: cint): cint {.importc.}
    echo add(1, 2)
    
    
    Run

Actually you can do this in pure Nim, something like:
    
    
    import hashes
    
    const cfile = "testing.c"
    const chash* = staticRead(cfile).hash()
    {.emit: "#include <testing.c>".}
    proc cversion*(): Hash {.exportc: "cversion_" & $cfile.hash() & "_" & 
$chash.} =
      ## hack to force Nim to keep this
      chash
    
    proc add*(a, b: cint): cint {.importc.}
    proc add(a, b: cint): cint {.importc.}
    echo add(1, 2)
    
    
    Run

For completeness, the C file is:
    
    
    int add(int a, int b) {
      return a + b + 2000;
    }
    
    
    Run