add a debug subcommand for printing LLVM integer type alignment

Useful when debugging why upgrading from LLVM 17 to 18 caused C ABI
regressions. Turns out LLVM 18 does the following insane thing:

```diff
-[nix-shell:~/dev/zig/build-llvm17]$ stage4/bin/zig llvm-ints i386-linux-musl
+[nix-shell:~/src/zig/build-llvm18]$ stage4/bin/zig llvm-ints i386-linux-musl
 LLVMABIAlignmentOfType(i1) == 1
 LLVMABIAlignmentOfType(i8) == 1
 LLVMABIAlignmentOfType(i16) == 2
 LLVMABIAlignmentOfType(i32) == 4
 LLVMABIAlignmentOfType(i64) == 4
-LLVMABIAlignmentOfType(i128) == 4
-LLVMABIAlignmentOfType(i256) == 4
+LLVMABIAlignmentOfType(i128) == 16
+LLVMABIAlignmentOfType(i256) == 16
```

src/codegen/llvm/bindings.zig

@@ -43,6 +43,9 @@ pub const Context = opaque {
 
     pub const getBrokenDebugInfo = ZigLLVMGetBrokenDebugInfo;
     extern fn ZigLLVMGetBrokenDebugInfo(C: *Context) bool;
+
+    pub const intType = LLVMIntTypeInContext;
+    extern fn LLVMIntTypeInContext(C: *Context, NumBits: c_uint) *Type;
 };
 
 pub const Module = opaque {
@@ -96,13 +99,21 @@ pub const TargetMachine = opaque {
         llvm_ir_filename: ?[*:0]const u8,
         bitcode_filename: ?[*:0]const u8,
     ) bool;
+
+    pub const createTargetDataLayout = LLVMCreateTargetDataLayout;
+    extern fn LLVMCreateTargetDataLayout(*TargetMachine) *TargetData;
 };
 
 pub const TargetData = opaque {
     pub const dispose = LLVMDisposeTargetData;
     extern fn LLVMDisposeTargetData(*TargetData) void;
+
+    pub const abiAlignmentOfType = LLVMABIAlignmentOfType;
+    extern fn LLVMABIAlignmentOfType(TD: *TargetData, Ty: *Type) c_uint;
 };
 
+pub const Type = opaque {};
+
 pub const CodeModel = enum(c_int) {
     Default,
     JITDefault,