[K/N] Add workaround for KT-48591

The root case for the bug is that we import runtime functions with
signext parameters, but KChars are zeroext. Workaround this mismatch
by fixing signatures of functions that we consider "dangerous".

The correct fix will be too big to be included in 1.5.31 and 1.6.0.

kotlin-native/runtime/src/main/cpp/KString.cpp

@@ -300,11 +300,11 @@ KBoolean Kotlin_Char_isISOControl(KChar ch) {
   return (ch <= 0x1F) || (ch >= 0x7F && ch <= 0x9F);
 }
 
-KBoolean Kotlin_Char_isHighSurrogate(KChar ch) {
+KBoolean Kotlin_Char_isHighSurrogate(KCharSignExt ch) {
   return ((ch & 0xfc00) == 0xd800);
 }
 
-KBoolean Kotlin_Char_isLowSurrogate(KChar ch) {
+KBoolean Kotlin_Char_isLowSurrogate(KCharSignExt ch) {
   return ((ch & 0xfc00) == 0xdc00);
 }
 

kotlin-native/runtime/src/main/cpp/Types.h

@@ -43,6 +43,10 @@
 typedef bool KBoolean;
 typedef int8_t  KByte;
 typedef uint16_t KChar;
+/**
+ * Hack for KT-48591.
+ */
+typedef int16_t KCharSignExt;
 typedef int16_t KShort;
 typedef int32_t KInt;
 typedef int64_t KLong;