Improve nimeval, changes some defaults (#14351)

* Improve nimeval, changes some defaults

This improves nimeval to make it easier to use NimScript as an embedded
scripting languages. It does change some of the defaults, so in case
anything used the old version and depended on the old behaviour these
would have to be changed.

* Remove dependency on nimhcr for nimscript

compiler/nimeval.nim

@@ -99,14 +99,16 @@ proc findNimStdLibCompileTime*(): string =
 
 proc createInterpreter*(scriptName: string;
                         searchPaths: openArray[string];
-                        flags: TSandboxFlags = {}): Interpreter =
+                        flags: TSandboxFlags = {},
+                        defines = @[("nimscript", "true")],
+                        registerOps = true): Interpreter =
   var conf = newConfigRef()
   var cache = newIdentCache()
   var graph = newModuleGraph(cache, conf)
   connectCallbacks(graph)
   initDefines(conf.symbols)
-  defineSymbol(conf.symbols, "nimscript")
+  for define in defines:
-  defineSymbol(conf.symbols, "nimconfig")
+    defineSymbol(conf.symbols, define[0], define[1])
   registerPass(graph, semPass)
   registerPass(graph, evalPass)
 
@@ -119,6 +121,8 @@ proc createInterpreter*(scriptName: string;
   var vm = newCtx(m, cache, graph)
   vm.mode = emRepl
   vm.features = flags
+  if registerOps:
+    vm.registerAdditionalOps() # Required to register parts of stdlib modules
   graph.vm = vm
   graph.compileSystemModule()
   result = Interpreter(mainModule: m, graph: graph, scriptName: scriptName)

lib/system.nim

@@ -3026,5 +3026,5 @@ export widestrs
 import system/io
 export io
 
-when not defined(createNimHcr):
+when not defined(createNimHcr) and not defined(nimscript):
   include nimhcr