Adopt no-std tests to new preacllocated_* functions

Author: elichai

no_std_test/src/main.rs

@@ -53,6 +53,7 @@ use core::intrinsics;
 use core::panic::PanicInfo;
 
 use secp256k1::ecdh::SharedSecret;
+use secp256k1::ffi::types::AlignedType;
 use secp256k1::rand::{self, RngCore};
 use secp256k1::serde::Serialize;
 use secp256k1::*;
@@ -82,7 +83,7 @@ impl RngCore for FakeRng {
 
 #[start]
 fn start(_argc: isize, _argv: *const *const u8) -> isize {
-    let mut buf = [0u8; 600_000];
+    let mut buf = [AlignedType::zeroed(); 37_000];
     let size = Secp256k1::preallocate_size();
     unsafe { libc::printf("needed size: %d\n\0".as_ptr() as _, size) };
 
@@ -161,5 +162,5 @@ fn panic(info: &PanicInfo) -> ! {
     let mut buf = Print::new();
     write(&mut buf, *msg).unwrap();
     buf.print();
-    unsafe { intrinsics::abort() }
+    intrinsics::abort()
 }