fix wrong result for putc variants due to operator precedence
the internal putc_unlocked macro was wrongly returning a meaningless
boolean result rather than the written character or EOF.
bug was found by reading (very surprising) asm.
diff --git a/src/internal/stdio_impl.h b/src/internal/stdio_impl.h
index ab34da2..4449734 100644
--- a/src/internal/stdio_impl.h
+++ b/src/internal/stdio_impl.h
@@ -105,7 +105,7 @@
( ((f)->rpos != (f)->rend) ? *(f)->rpos++ : __uflow((f)) )
#define putc_unlocked(c, f) \
- ( ((unsigned char)(c)!=(f)->lbf && (f)->wpos!=(f)->wend) \
+ ( (((unsigned char)(c)!=(f)->lbf && (f)->wpos!=(f)->wend)) \
? *(f)->wpos++ = (c) : __overflow((f),(c)) )
/* Caller-allocated FILE * operations */