Prefer to find icu via pkg-config instead of icu-config. Honor the CXXFLAGS that
are indicated by either of those tools. Work around new ICU requirement that a
namespace be used by specifying the flag that overrides that requirement.

Includes relevant parts of the following upstream commits:

DateFormat plays nice with Calendar, TimeZone
(just the part that fixes the extern "C" issues)
https://github.com/php/php-src/commit/eb346ef0f419b90739aadfb6cc7b7436c5b521d9

fix typo
https://github.com/php/php-src/commit/977974f95fa5b76f7e0e9d29e39c0dc52dfaa913

Fix typo
https://github.com/php/php-src/commit/50b38322b96416b0a5609591a52178f6100768da

Fix #73956 Link use CC instead of CXX
https://github.com/php/php-src/commit/6af22d0d3ed224d89be1d1e9e53ff7e2e2e5439d

Fixed bug #76153 Intl compilation fails with icu4c 61.1
https://github.com/php/php-src/commit/710284cbc4a54cac0a9ec4ea29a7486e0d99a33b

Fix clang build, ref buf #76153
https://github.com/php/php-src/commit/8b104d789317d96f6d3e23e635f0ca288c0a23ee

Fix shared ext/intl compilation
https://github.com/php/php-src/commit/2bd299f7318492fd7e5cafffa562d76ba60e69d4

Rename var
https://github.com/php/php-src/commit/ed5aabe8b78d8487ffc6091e0670753d59bb7f5a

Group common flags
https://github.com/php/php-src/commit/09d7ffabcd99fe9b99c4206f321fecc506635072
--- ext/intl/collator/collator.h.orig	2015-09-01 15:09:37.000000000 -0500
+++ ext/intl/collator/collator.h	2019-10-23 19:13:42.000000000 -0500
@@ -16,7 +16,7 @@
  */
 
 #ifndef COLLATOR_COLLATOR_H
-#define CCOLLATOR_COLLATOR_H
+#define COLLATOR_COLLATOR_H
 
 #include <php.h>
 
--- ext/intl/collator/collator_attr.h.orig	2015-09-01 15:09:37.000000000 -0500
+++ ext/intl/collator/collator_attr.h	2019-10-23 19:13:42.000000000 -0500
@@ -16,7 +16,7 @@
  */
 
 #ifndef COLLATOR_ATTR_H
-#define CCOLLATOR_ATTR_H
+#define COLLATOR_ATTR_H
 
 #include <php.h>
 
--- ext/intl/config.m4.orig	2014-08-13 14:22:50.000000000 -0500
+++ ext/intl/config.m4	2019-10-23 19:24:09.000000000 -0500
@@ -9,6 +9,7 @@
   PHP_SETUP_ICU(INTL_SHARED_LIBADD)
   PHP_SUBST(INTL_SHARED_LIBADD)
   PHP_REQUIRE_CXX()
+  INTL_COMMON_FLAGS="$ICU_INCS"
 
   PHP_NEW_EXTENSION(intl, php_intl.c \
     intl_error.c \
@@ -48,14 +49,21 @@
     msgformat/msgformat_class.c \
     msgformat/msgformat_data.c  \
     msgformat/msgformat_format.c \
-    msgformat/msgformat_helpers.cpp \
     msgformat/msgformat_parse.c \
     grapheme/grapheme_string.c \
     grapheme/grapheme_util.c \
     resourcebundle/resourcebundle.c \
     resourcebundle/resourcebundle_class.c \
     resourcebundle/resourcebundle_iterator.c \
-    idn/idn.c, $ext_shared,,$ICU_INCS)
+    idn/idn.c, $ext_shared,,$INTL_COMMON_FLAGS,cxx)
+
+  PHP_INTL_CXX_SOURCES="msgformat/msgformat_helpers.cpp"
+  PHP_INTL_CXX_FLAGS="$INTL_COMMON_FLAGS $ICU_CXXFLAGS"
+  if test "$ext_shared" = "no"; then
+    PHP_ADD_SOURCES(PHP_EXT_DIR(intl), $PHP_INTL_CXX_SOURCES, $PHP_INTL_CXX_FLAGS)
+  else
+    PHP_ADD_SOURCES_X(PHP_EXT_DIR(intl), $PHP_INTL_CXX_SOURCES, $PHP_INTL_CXX_FLAGS, shared_objects_intl, yes)
+  fi
 
   PHP_ADD_BUILD_DIR($ext_builddir/collator)
   PHP_ADD_BUILD_DIR($ext_builddir/common)
--- ext/intl/grapheme/grapheme.h.orig	2015-09-01 15:09:37.000000000 -0500
+++ ext/intl/grapheme/grapheme.h	2019-10-23 19:13:35.000000000 -0500
@@ -19,7 +19,6 @@
 
 #include <php.h>
 #include <unicode/utypes.h>
-#include <unicode/ubrk.h>
 
 PHP_FUNCTION(grapheme_strlen);
 PHP_FUNCTION(grapheme_strpos);
--- ext/intl/php_intl.c.orig	2015-09-01 15:09:37.000000000 -0500
+++ ext/intl/php_intl.c	2019-10-23 19:13:35.000000000 -0500
@@ -41,6 +41,8 @@
 #include "formatter/formatter_main.h"
 #include "formatter/formatter_parse.h"
 
+#include "grapheme/grapheme.h"
+
 #include "msgformat/msgformat.h"
 #include "msgformat/msgformat_class.h"
 #include "msgformat/msgformat_attr.h"
--- ext/intl/php_intl.h.orig	2015-09-01 15:09:37.000000000 -0500
+++ ext/intl/php_intl.h	2019-10-23 19:13:35.000000000 -0500
@@ -22,8 +22,13 @@
 
 #include <php.h>
 
+/* Even if we're included from C++, don't introduce C++ definitions
+ * because we were included with extern "C". The effect would be that
+ * when the headers defined any method, they would do so with C linkage */
+#undef U_SHOW_CPLUSPLUS_API
+#define U_SHOW_CPLUSPLUS_API 0
 #include "collator/collator_sort.h"
-#include "grapheme/grapheme.h"
+#include <unicode/ubrk.h>
 #include "intl_error.h"
 
 extern zend_module_entry intl_module_entry;
