Fuse primitive equality with safe call to avoid boxing

In code like 'a?.b == 42', we can immediately generate equality
comparison result when receiver is null (false for '==', true for '!='),
since the primitive value is definitely non-null.
Otherwise unnecessary boxing/unboxing is generated to handle possibly
null result of 'a?.b'.

compiler/testData/codegen/bytecodeText/boxingOptimization/safeCallToPrimitiveEquality.kt

@@ -0,0 +1,23 @@
+fun Long.id() = this
+
+fun String.drop2() = if (length >= 2) subSequence(2, length) else null
+
+fun doSimple1(s: String?) = s?.length == 3
+
+fun doLongReceiver1(x: Long) = x?.id() == 3L
+
+fun doChain1(s: String?) = s?.drop2()?.length == 1
+
+fun doIf1(s: String?) =
+        if (s?.length == 1) "A" else "B"
+
+fun doSimple2(s: String?) = 3 == s?.length
+
+fun doLongReceiver2(x: Long) = 3L == x?.id()
+
+fun doChain2(s: String?) = 1 == s?.drop2()?.length
+
+fun doIf2(s: String?) =
+        if (1 == s?.length) "A" else "B"
+
+// 0 valueOf