Fix #1684 by bringing in GaloisInc/crucible#998

Now that the `crucible-llvm` memory model can reason about struct padding
with `lax-loads-and-stores` enabled, bumping the `crucible` submodule to bring
in that change fixes #1684 as a consequence. I have also added a regression
test.

Author: RyanGlScott

deps/crucible

@@ -0,0 +1,11 @@
+CC = clang
+CFLAGS = -g -emit-llvm -frecord-command-line -O0
+
+all: test.bc
+
+test.bc: test.c
+	$(CC) $(CFLAGS) -c $< -o $@
+
+.PHONY: clean
+clean:
+	rm -f test.bc

deps/macaw

@@ -0,0 +1,12 @@
+#include <stdint.h>
+
+struct a {
+  uint16_t x;
+  uint32_t y;
+};
+
+struct b {
+  struct a aa;
+};
+
+void f(struct b *bb) {}

intTests/test1684/Makefile

@@ -0,0 +1,13 @@
+enable_experimental;
+enable_lax_loads_and_stores;
+
+let f_spec = do {
+  aa <- llvm_fresh_var "aa" (llvm_alias "struct.a");
+  bb <- llvm_alloc (llvm_alias "struct.b");
+  llvm_points_to (llvm_field bb "aa") (llvm_term aa);
+
+  llvm_execute_func [bb];
+};
+
+m <- llvm_load_module "test.bc";
+llvm_verify m "f" [] false f_spec (w4_unint_yices []);

intTests/test1684/test.bc

@@ -0,0 +1,3 @@
+set -e
+
+$SAW test.saw