bugfixes; field discriminant checks; linearScanEnd, unroll, shallow pragmas

tests/accept/compile/tlinearscanend.nim

@@ -0,0 +1,24 @@
+
+import strutils
+
+var x = 343
+
+case stdin.readline.parseInt
+of 0: 
+  echo "most common case"
+of 1: 
+  {.linearScanEnd.}
+  echo "second most common case"
+of 2: echo "unlikely: use branch table"
+else: 
+  echo "unlikely too: use branch table"
+
+
+case x
+of 23: echo "23"
+of 343: echo "343"
+of 21: echo "21"
+else: 
+  {.linearScanEnd.}
+  echo "default"
+

tests/accept/compile/ttypeconverter1.nim

@@ -0,0 +1,6 @@
+
+converter p(i: int): bool = return i != 0
+
+if 0:
+  echo "foo"
+