[MERGE #4952 @kfarnung] Set U_USING_ICU_NAMESPACE to 0 by default

Merge pull request #4952 from kfarnung:icu61

ICU61 updated the value of `U_USING_ICU_NAMESPACE` to 0 by default. In
order to maintain compatibility this change updates our ICU includes to
match and adds the `icu::` namespace explicitly when needed.

Refs: nodejs/node#18667
Refs: https://ssl.icu-project.org/trac/ticket/13460

Author: kfarnung

lib/Runtime/Library/RuntimeLibraryPch.h

@@ -101,6 +101,7 @@
 #ifdef INTL_ICU
 #define U_STATIC_IMPLEMENTATION
 #define U_SHOW_CPLUSPLUS_API 0
+#define U_USING_ICU_NAMESPACE 0
 #pragma warning(push)
 #pragma warning(disable:4995)
 #include <unicode/uloc.h>

lib/Runtime/PlatformAgnostic/Platform/Common/Intl.cpp

@@ -46,6 +46,7 @@ typedef uint64_t uint64;
 
 #define U_STATIC_IMPLEMENTATION
 #define U_SHOW_CPLUSPLUS_API 1
+#define U_USING_ICU_NAMESPACE 0
 #pragma warning(push)
 #pragma warning(disable:4995) // deprecation warning
 #include <unicode/uloc.h>

lib/Runtime/PlatformAgnostic/Platform/Linux/UnicodeText.ICU.cpp

@@ -6,6 +6,7 @@
 #include "RuntimePlatformAgnosticPch.h"
 #include "UnicodeText.h"
 #ifdef HAS_REAL_ICU
+#define U_USING_ICU_NAMESPACE 0
 #include <unicode/uchar.h>
 #include <unicode/ustring.h>
 #include <unicode/normalizer2.h>
@@ -31,24 +32,24 @@ namespace PlatformAgnostic
 
 #ifdef HAS_REAL_ICU
         // Helper ICU conversion facilities
-        static const Normalizer2* TranslateToICUNormalizer(NormalizationForm normalizationForm)
+        static const icu::Normalizer2* TranslateToICUNormalizer(NormalizationForm normalizationForm)
         {
             UErrorCode errorCode = U_ZERO_ERROR;
-            const Normalizer2* normalizer;
+            const icu::Normalizer2* normalizer;
 
             switch (normalizationForm)
             {
                 case NormalizationForm::C:
-                    normalizer = Normalizer2::getNFCInstance(errorCode);
+                    normalizer = icu::Normalizer2::getNFCInstance(errorCode);
                     break;
                 case NormalizationForm::D:
-                    normalizer = Normalizer2::getNFDInstance(errorCode);
+                    normalizer = icu::Normalizer2::getNFDInstance(errorCode);
                     break;
                 case NormalizationForm::KC:
-                    normalizer = Normalizer2::getNFKCInstance(errorCode);
+                    normalizer = icu::Normalizer2::getNFKCInstance(errorCode);
                     break;
                 case NormalizationForm::KD:
-                    normalizer = Normalizer2::getNFKDInstance(errorCode);
+                    normalizer = icu::Normalizer2::getNFKDInstance(errorCode);
                     break;
                 default:
                     AssertMsg(false, "Unsupported normalization form");
@@ -157,13 +158,13 @@ namespace PlatformAgnostic
                 return -1 * invalidIndex; // mimicking the behavior of Win32 NormalizeString
             }
 
-            const Normalizer2* normalizer = TranslateToICUNormalizer(normalizationForm);
+            const icu::Normalizer2* normalizer = TranslateToICUNormalizer(normalizationForm);
             Assert(normalizer != nullptr);
 
-            const UnicodeString sourceUniStr((const UChar*) sourceString, sourceLength);
+            const icu::UnicodeString sourceUniStr((const UChar*) sourceString, sourceLength);
 
             UErrorCode errorCode = U_ZERO_ERROR;
-            const UnicodeString destUniStr = normalizer->normalize(sourceUniStr, errorCode);
+            const icu::UnicodeString destUniStr = normalizer->normalize(sourceUniStr, errorCode);
 
             if (U_FAILURE(errorCode))
             {
@@ -208,10 +209,10 @@ namespace PlatformAgnostic
                 return false;
             }
 
-            const Normalizer2* normalizer = TranslateToICUNormalizer(normalizationForm);
+            const icu::Normalizer2* normalizer = TranslateToICUNormalizer(normalizationForm);
             Assert(normalizer != nullptr);
 
-            const UnicodeString testUniStr((const UChar*) testString, length);
+            const icu::UnicodeString testUniStr((const UChar*) testString, length);
             bool isNormalized = normalizer->isNormalized(testUniStr, errorCode);
 
             Assert(U_SUCCESS(errorCode));

lib/Runtime/PlatformAgnostic/RuntimePlatformAgnosticPch.h

@@ -34,6 +34,7 @@
 #define FALSE 0
 #endif
 #else
+#define U_USING_ICU_NAMESPACE 0
 #include <unicode/umachine.h>
 #endif