hush: make read builtin interruptible.

function                                             old     new   delta
builtin_read                                         185     471    +286
check_and_run_traps                                  200     262     +62
nonblock_immune_read                                  73     119     +46
sigismember                                            -      44     +44
record_signal                                          -      21     +21
sigisemptyset                                          -      16     +16
...
------------------------------------------------------------------------------
(add/remove: 5/0 grow/shrink: 7/5 up/down: 483/-46)           Total: 437 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/include/libbb.h b/include/libbb.h
index 4ea94e7..56dfa61 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -672,7 +672,7 @@
 
 
 extern ssize_t safe_read(int fd, void *buf, size_t count) FAST_FUNC;
-extern ssize_t nonblock_immune_read(int fd, void *buf, size_t count) FAST_FUNC;
+extern ssize_t nonblock_immune_read(int fd, void *buf, size_t count, int loop_on_EINTR) FAST_FUNC;
 // NB: will return short read on error, not -1,
 // if some data was read before error occurred
 extern ssize_t full_read(int fd, void *buf, size_t count) FAST_FUNC;