Fix warnings in chained volatile assignments

[ericpassmore]

A test contract declares variables as volatile and then uses them in a chained assignments. This isn't supported, and not sure why the contract is constructed this way.

cdt/tests/unit/test_contracts/malloc_tests.cpp

Lines 27 to 49 in a0e7748

	ptr6[0] = ptr6[1] = ((__int128_t(0x7777777777777777) << 64) | 0x7777777777777777);
	volatile __int128_t *ptr7 = (__int128_t*)malloc(sizeof(__int128_t) * 2);
	ptr7[0] = ptr7[1] = ((__int128_t(0x8888888888888888) << 64) | 0x8888888888888888);
	volatile long long *ptr8 = (long long*)malloc(sizeof(long long) * 3);
	ptr8[0] = ptr8[1] = ptr8[2] = 0x9999999999999999;
	volatile long long *ptr9 = (long long*)malloc(sizeof(long long) * 3);
	ptr9[0] = ptr9[1] = ptr9[2] = 0xAAAAAAAAAAAAAAAA;
	eosio::check(*ptr0 == 0x11, "wrong value for char");
	eosio::check(*ptr1 == 0x2222, "wrong value for short");
	eosio::check(*ptr2 == 0x33333333, "wrong value for int");
	eosio::check(*ptr3 == 0x4444444444444444, "wrong value for long long");
	eosio::check(*ptr4 == ((__int128_t(0x5555555555555555) << 64) | 0x5555555555555555), "wrong value for __int128 #1");
	eosio::check(*ptr5 == ((__int128_t(0x6666666666666666) << 64) | 0x6666666666666666), "wrong value for __int128 #2");
	eosio::check(ptr6[0] == ((__int128_t(0x7777777777777777) << 64) | 0x7777777777777777), "wrong value for __int128[2] #1");
	eosio::check(ptr6[1] == ((__int128_t(0x7777777777777777) << 64) | 0x7777777777777777), "wrong value for __int128[2] #1");
	eosio::check(ptr7[0] == ((__int128_t(0x8888888888888888) << 64) | 0x8888888888888888), "wrong value for __int128[2] #2");
	eosio::check(ptr7[1] == ((__int128_t(0x8888888888888888) << 64) | 0x8888888888888888), "wrong value for __int128[2] #2");
	eosio::check(ptr8[0] == 0x9999999999999999, "wrong value for long long[3] #1");
	eosio::check(ptr8[1] == 0x9999999999999999, "wrong value for long long[3] #1");
	eosio::check(ptr8[2] == 0x9999999999999999, "wrong value for long long[3] #1");
	eosio::check(ptr9[0] == 0xAAAAAAAAAAAAAAAA, "wrong value for long long[3] #2");
	eosio::check(ptr9[1] == 0xAAAAAAAAAAAAAAAA, "wrong value for long long[3] #2");
	eosio::check(ptr9[2] == 0xAAAAAAAAAAAAAAAA, "wrong value for long long[3] #2");