Implemented break and continue and improved label stack handling

flagpole/tests/break.fp

@@ -0,0 +1,11 @@
+$inc fvmstd.fp
+
+proc main
+  while 1 do
+    if :getuint 37 == then
+      break
+    endif
+    "Try again" :puts :newline
+  endwhile
+  "You got it!" :puts :newline
+endproc

flagpole/tests/continue.fp

@@ -0,0 +1,20 @@
+$inc fvmstd.fp
+
+proc main
+  while 1 do
+    if :getuint 37 == not then
+      "Number 1 incorrect" :puts :newline
+      continue
+    endif
+    if :getuint 42 == not then
+      "Number 2 incorrect" :puts :newline
+      continue
+    endif
+    if :getuint 69 == not then
+      "Number 3 incorrect" :puts :newline
+      continue
+    endif
+    break
+  endwhile
+  "You've logged in" :puts :newline
+endproc