awk: disallow break/continue outside of loops

function                                             old     new   delta
.rodata                                           104139  104186     +47
chain_group                                          610     633     +23
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/0 up/down: 70/0)               Total: 70 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>