Add CtsIcu4cTestCases for ICU4C API coverage - Attempt 2

Attempt 2: The test is only for primary ABI, until the Soong limitation
is resolved.
- cintltest and intltest are the executable binaries
  running the devices.
- cintltest and intltest are basically compiled against
  libicuuc and libicui18n, except if the APIs are available
  in the NDK surface in libicu, the test will link that in favour
  of NDK. So the APIs provided in the NDK will have the API coverge,
  while the test can keep using the hidden APIs in libicuuc, and
  libicui18n.
  cts_headers/ are the same as libicuuc and libicui18n headers, except
  that unicode/urename.h is modified by the generate_ndk.py to select
  the NDK API surface.

Bug: 160350521
Test: atest CtsIcu4cTestCases
Test: Inspect the symbol table manually by "objdump -TC cintltst"
Test: build/soong/build_test.bash
Test: Test: OUT_DIR=ndk_out build/soong/scripts/build-ndk-prebuilts.sh
Change-Id: Icf51b09c36eb3b4ef30a5032bdef7af1a76567d9
diff --git a/libicu/cts_headers/locmap.h b/libicu/cts_headers/locmap.h
new file mode 100644
index 0000000..e669873
--- /dev/null
+++ b/libicu/cts_headers/locmap.h
@@ -0,0 +1,40 @@
+// © 2016 and later: Unicode, Inc. and others.
+// License & terms of use: http://www.unicode.org/copyright.html
+/*
+******************************************************************************
+*
+*   Copyright (C) 1996-2013, International Business Machines
+*   Corporation and others.  All Rights Reserved.
+*
+******************************************************************************
+*
+* File locmap.h      : Locale Mapping Classes
+* 
+*
+* Created by: Helena Shih
+*
+* Modification History:
+*
+*  Date        Name        Description
+*  3/11/97     aliu        Added setId().
+*  4/20/99     Madhu       Added T_convertToPosix()
+* 09/18/00     george      Removed the memory leaks.
+* 08/23/01     george      Convert to C
+*============================================================================
+*/
+
+#ifndef LOCMAP_H
+#define LOCMAP_H
+
+#include "unicode/utypes.h"
+
+#define LANGUAGE_LCID(hostID) (uint16_t)(0x03FF & hostID)
+
+U_CAPI int32_t uprv_convertToPosix(uint32_t hostid, char* posixID, int32_t posixIDCapacity, UErrorCode* status);
+
+/* Don't call these functions directly. Use uloc_getLCID instead. */
+U_CAPI uint32_t uprv_convertToLCIDPlatform(const char* localeID, UErrorCode* status); // Leverage platform conversion if possible
+U_CAPI uint32_t uprv_convertToLCID(const char* langID, const char* posixID, UErrorCode* status);
+
+#endif /* LOCMAP_H */
+