DrNim (Nim compiler with Z3 integration) (#13743)

* code cleanups and feature additions
* added basic test and koch/CI integration
* make it build on Unix
* DrNim: now buildable on Unix, only takes 10 minutes, enjoy
* added basic documentation for DrNim which can also be seen as the RFC we're following
* drnim: change the build setup so that drnim.exe ends up in bin/
* makes simple floating point ranges work
* added basic float range check
* drnim: teach Z3 about Nim's range types plus code refactoring
* drnim: make unsigned numbers work
* added and fixed index checking under setLen
* first implementation of .ensures, .invariant and .assume (.requires still missing and so is proc type compatibility checking
* drnim: .requires checking implemented
* drnim: implemented .ensures properly
* more impressive test involving min()
* drnim: check for proc type compatibility and base method compatibility wrt .requires and .ensures
* testament: support for 'pattern <directory>
* koch: uses new <directory> feature of testament
* drnim: added tiny musings about 'old'
* Make testament work with old SSL versions
* koch: add support for 'koch drnim -d:release'
* drnim: preparations for the param.old notation

compiler/wordrecg.nim

@@ -54,6 +54,7 @@ type
     wNonReloadable, wExecuteOnReload,
     wAssertions, wPatterns, wTrMacros, wSinkInference, wWarnings,
     wHints, wOptimization, wRaises, wWrites, wReads, wSize, wEffects, wTags,
+    wRequires, wEnsures, wInvariant, wAssume,
     wDeadCodeElimUnused,  # deprecated, dead code elim always happens
     wSafecode, wPackage, wNoForward, wReorder, wNoRewrite, wNoDestroy,
     wPragma,
@@ -142,6 +143,7 @@ const
 
     "assertions", "patterns", "trmacros", "sinkinference", "warnings", "hints",
     "optimization", "raises", "writes", "reads", "size", "effects", "tags",
+    "requires", "ensures", "invariant", "assume",
     "deadcodeelim",  # deprecated, dead code elim always happens
     "safecode", "package", "noforward", "reorder", "norewrite", "nodestroy",
     "pragma",