stage2: add support for integers in LLVM backend

Also adds support for simple operators, like add and subtract.
The intcast and bitcast instruction also have been implemented.

Linking with libc also works, so we can now generate working executables!

`zig build-exe example.zig -fLLVM -lc`:
```
fn add(a: i32, b: i32) i32 {
    return a + b;
}

export fn main() c_int {
    var a: i32 = -5;
    const x = add(a, 7);
    var y = add(2, 0);
    y -= x;
    return y;
}
```

1 files changed, 27 insertions, 0 deletions

diff --git a/src/llvm_bindings.zig b/src/llvm_bindings.zig
index 9198cc714b..aa95537328 100644
--- a/src/llvm_bindings.zig
+++ b/src/llvm_bindings.zig
@@ -43,8 +43,14 @@ pub const TypeRef = opaque {
     pub const constAllOnes = LLVMConstAllOnes;
     extern fn LLVMConstAllOnes(Ty: *const TypeRef) *const ValueRef;
 
+    pub const constInt = LLVMConstInt;
+    extern fn LLVMConstInt(IntTy: *const TypeRef, N: c_ulonglong, SignExtend: LLVMBool) *const ValueRef;
+
     pub const getUndef = LLVMGetUndef;
     extern fn LLVMGetUndef(Ty: *const TypeRef) *const ValueRef;
+
+    pub const pointerType = LLVMPointerType;
+    extern fn LLVMPointerType(ElementType: *const TypeRef, AddressSpace: c_uint) *const TypeRef;
 };
 
 pub const ModuleRef = opaque {
@@ -82,6 +88,9 @@ pub const VerifierFailureAction = extern enum {
     ReturnStatus,
 };
 
+pub const constNeg = LLVMConstNeg;
+extern fn LLVMConstNeg(ConstantVal: *const ValueRef) *const ValueRef;
+
 pub const voidType = LLVMVoidType;
 extern fn LLVMVoidType() *const TypeRef;
 
@@ -143,6 +152,24 @@ pub const BuilderRef = opaque {
 
     pub const buildNot = LLVMBuildNot;
     extern fn LLVMBuildNot(*const BuilderRef, V: *const ValueRef, Name: [*:0]const u8) *const ValueRef;
+
+    pub const buildNSWAdd = LLVMBuildNSWAdd;
+    extern fn LLVMBuildNSWAdd(*const BuilderRef, LHS: *const ValueRef, RHS: *const ValueRef, Name: [*:0]const u8) *const ValueRef;
+
+    pub const buildNUWAdd = LLVMBuildNUWAdd;
+    extern fn LLVMBuildNUWAdd(*const BuilderRef, LHS: *const ValueRef, RHS: *const ValueRef, Name: [*:0]const u8) *const ValueRef;
+
+    pub const buildNSWSub = LLVMBuildNSWSub;
+    extern fn LLVMBuildNSWSub(*const BuilderRef, LHS: *const ValueRef, RHS: *const ValueRef, Name: [*:0]const u8) *const ValueRef;
+
+    pub const buildNUWSub = LLVMBuildNUWSub;
+    extern fn LLVMBuildNUWSub(*const BuilderRef, LHS: *const ValueRef, RHS: *const ValueRef, Name: [*:0]const u8) *const ValueRef;
+
+    pub const buildIntCast2 = LLVMBuildIntCast2;
+    extern fn LLVMBuildIntCast2(*const BuilderRef, Val: *const ValueRef, DestTy: *const TypeRef, IsSigned: LLVMBool, Name: [*:0]const u8) *const ValueRef;
+
+    pub const buildBitCast = LLVMBuildBitCast;
+    extern fn LLVMBuildBitCast(*const BuilderRef, Val: *const ValueRef, DestTy: *const TypeRef, Name: [*:0]const u8) *const ValueRef;
 };
 
 pub const BasicBlockRef = opaque {