A motivating example for the new bindSym behavior.

The example is a proof-of-concept logging library, allowing you to define
lexically-scoped environments where certain logging attributes are applied
automatically to all logging statements.

fixes tmacro1 (use of `bindSym` inside static blocks)

compiler/semdata.nim

@@ -89,6 +89,7 @@ type
     ambiguousSymbols*: IntSet  # ids of all ambiguous symbols (cannot
                                # store this info in the syms themselves!)
     inGenericContext*: int     # > 0 if we are in a generic type
+    inStaticContext*: int      # > 0 if we are inside a static: block
     inUnrolledContext*: int    # > 0 if we are unrolling a loop
     compilesContextId*: int    # > 0 if we are in a ``compiles`` magic
     compilesContextIdGenerator*: int