abi: rename malloc into proxy_on_memory_allocate to make `cargo w…

…asi test` work (#2)

src/allocator.rs

@@ -16,7 +16,7 @@
 static ALLOC: wee_alloc::WeeAlloc = wee_alloc::WeeAlloc::INIT;
 
 #[no_mangle]
-pub extern "C" fn malloc(size: usize) -> *mut u8 {
+pub extern "C" fn proxy_on_memory_allocate(size: usize) -> *mut u8 {
     let mut vec: Vec<u8> = Vec::with_capacity(size);
     unsafe {
         vec.set_len(size);