Convert all zero-argument functions to '(void)'

Otherwise, in C, it becomes a K&R function declaration which doesn't actually
type-check the number of arguments.

Change-Id: I0731a9fefca46fb1c266bfb1c33d464cf451a22e
Reviewed-on: https://boringssl-review.googlesource.com/1582
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/crypto/x509v3/tabtest.c b/crypto/x509v3/tabtest.c
index aa27c1e..06a692e 100644
--- a/crypto/x509v3/tabtest.c
+++ b/crypto/x509v3/tabtest.c
@@ -66,7 +66,7 @@
 
 #include "ext_dat.h"
 
-int main()
+int main(void)
 {
 	int i, prev = -1, bad = 0;
 	const X509V3_EXT_METHOD **tmp;