use inline functions instead of casting function pointers

the type casts we were using were causing bad things to happen with gcc builds (still not exactly sure
why they aren't in clang builds), since we were casting from a function which expects arguments on the stack
to a function type that doesn't.

this manifests itself as rewrite_args changing from NULL to a small heap pointer on this line:

```
objmodel.cpp:4108    contained = callattrInternal1(rhs, contains_str, CLASS_ONLY, NULL, ArgPassSpec(1), lhs);
```

that is, the local variable rewrite_args is NULL before the call, and non-NULL after.  The actual line that causes
the pointer overwrite is in `bindObjIntoArgs`:

```
objmodel.cpp:3043    arg1 = bind_obj;
```

so I'm guessing that since we didn't push things onto the stack before the call to `callattrInternal`, we end up
trampling over values in `compareInternal`'s frame.

src/runtime/objmodel.cpp

@@ -86,14 +86,20 @@ void REWRITE_ABORTED(const char* reason) {
 #define REWRITE_ABORTED(reason) ((void)(reason))
 #endif
 
-static Box* (*runtimeCallInternal0)(Box*, CallRewriteArgs*, ArgPassSpec)
-    = (Box * (*)(Box*, CallRewriteArgs*, ArgPassSpec))runtimeCallInternal;
-static Box* (*runtimeCallInternal1)(Box*, CallRewriteArgs*, ArgPassSpec, Box*)
-    = (Box * (*)(Box*, CallRewriteArgs*, ArgPassSpec, Box*))runtimeCallInternal;
-static Box* (*runtimeCallInternal2)(Box*, CallRewriteArgs*, ArgPassSpec, Box*, Box*)
-    = (Box * (*)(Box*, CallRewriteArgs*, ArgPassSpec, Box*, Box*))runtimeCallInternal;
-static Box* (*runtimeCallInternal3)(Box*, CallRewriteArgs*, ArgPassSpec, Box*, Box*, Box*)
-    = (Box * (*)(Box*, CallRewriteArgs*, ArgPassSpec, Box*, Box*, Box*))runtimeCallInternal;
+static inline Box* runtimeCallInternal0(Box* obj, CallRewriteArgs* rewrite_args, ArgPassSpec argspec) {
+    return runtimeCallInternal(obj, rewrite_args, argspec, NULL, NULL, NULL, NULL, NULL);
+}
+static inline Box* runtimeCallInternal1(Box* obj, CallRewriteArgs* rewrite_args, ArgPassSpec argspec, Box* arg1) {
+    return runtimeCallInternal(obj, rewrite_args, argspec, arg1, NULL, NULL, NULL, NULL);
+}
+static inline Box* runtimeCallInternal2(Box* obj, CallRewriteArgs* rewrite_args, ArgPassSpec argspec, Box* arg1,
+                                        Box* arg2) {
+    return runtimeCallInternal(obj, rewrite_args, argspec, arg1, arg2, NULL, NULL, NULL);
+}
+static inline Box* runtimeCallInternal3(Box* obj, CallRewriteArgs* rewrite_args, ArgPassSpec argspec, Box* arg1,
+                                        Box* arg2, Box* arg3) {
+    return runtimeCallInternal(obj, rewrite_args, argspec, arg1, arg2, arg3, NULL, NULL);
+}
 
 bool checkClass(LookupScope scope) {
     return (scope & CLASS_ONLY) != 0;
@@ -101,14 +107,23 @@ bool checkClass(LookupScope scope) {
 bool checkInst(LookupScope scope) {
     return (scope & INST_ONLY) != 0;
 }
-static Box* (*callattrInternal0)(Box*, BoxedString*, LookupScope, CallRewriteArgs*, ArgPassSpec)
-    = (Box * (*)(Box*, BoxedString*, LookupScope, CallRewriteArgs*, ArgPassSpec))callattrInternal;
-static Box* (*callattrInternal1)(Box*, BoxedString*, LookupScope, CallRewriteArgs*, ArgPassSpec, Box*)
-    = (Box * (*)(Box*, BoxedString*, LookupScope, CallRewriteArgs*, ArgPassSpec, Box*))callattrInternal;
-static Box* (*callattrInternal2)(Box*, BoxedString*, LookupScope, CallRewriteArgs*, ArgPassSpec, Box*, Box*)
-    = (Box * (*)(Box*, BoxedString*, LookupScope, CallRewriteArgs*, ArgPassSpec, Box*, Box*))callattrInternal;
-static Box* (*callattrInternal3)(Box*, BoxedString*, LookupScope, CallRewriteArgs*, ArgPassSpec, Box*, Box*, Box*)
-    = (Box * (*)(Box*, BoxedString*, LookupScope, CallRewriteArgs*, ArgPassSpec, Box*, Box*, Box*))callattrInternal;
+
+static inline Box* callattrInternal0(Box* obj, BoxedString* attr, LookupScope scope, CallRewriteArgs* rewrite_args,
+                                     ArgPassSpec argspec) {
+    return callattrInternal(obj, attr, scope, rewrite_args, argspec, NULL, NULL, NULL, NULL, NULL);
+}
+static inline Box* callattrInternal1(Box* obj, BoxedString* attr, LookupScope scope, CallRewriteArgs* rewrite_args,
+                                     ArgPassSpec argspec, Box* arg1) {
+    return callattrInternal(obj, attr, scope, rewrite_args, argspec, arg1, NULL, NULL, NULL, NULL);
+}
+static inline Box* callattrInternal2(Box* obj, BoxedString* attr, LookupScope scope, CallRewriteArgs* rewrite_args,
+                                     ArgPassSpec argspec, Box* arg1, Box* arg2) {
+    return callattrInternal(obj, attr, scope, rewrite_args, argspec, arg1, arg2, NULL, NULL, NULL);
+}
+static inline Box* callattrInternal3(Box* obj, BoxedString* attr, LookupScope scope, CallRewriteArgs* rewrite_args,
+                                     ArgPassSpec argspec, Box* arg1, Box* arg2, Box* arg3) {
+    return callattrInternal(obj, attr, scope, rewrite_args, argspec, arg1, arg2, arg3, NULL, NULL);
+}
 
 #if STAT_TIMERS
 static uint64_t* pyhasher_timer_counter = Stats::getStatCounter("us_timer_PyHasher");