Pass -std=c++11 when compiling files that include the ICU headers.  Without
this flag, compilation fails and causes Boost's build system to remove ICU
support.  Note that $(pkg-config --variable=CXXFLAGS icu-uc) includes
"-std=c++11", but Boost's build system does not use 'pkg-config'.

--- boost_1_66_0/libs/locale/build/Jamfile.v2.orig	2017-12-13 18:56:44.000000000 -0500
+++ boost_1_66_0/libs/locale/build/Jamfile.v2	2018-04-08 15:18:58.673025760 -0400
@@ -65,8 +65,8 @@
 
 if $(ICU_LINK)
 {
-    ICU_OPTS = <include>$(ICU_PATH)/include <linkflags>$(ICU_LINK) <dll-path>$(ICU_PATH)/bin <runtime-link>shared ;
-    ICU64_OPTS = <include>$(ICU_PATH)/include <linkflags>$(ICU_LINK) <dll-path>$(ICU_PATH)/bin64 <runtime-link>shared ;
+    ICU_OPTS = <include>$(ICU_PATH)/include <cxxflags>-std=c++11 <linkflags>$(ICU_LINK) <dll-path>$(ICU_PATH)/bin <runtime-link>shared ;
+    ICU64_OPTS = <include>$(ICU_PATH)/include <cxxflags>-std=c++11 <linkflags>$(ICU_LINK) <dll-path>$(ICU_PATH)/bin64 <runtime-link>shared ;
 }
 else
 {
@@ -121,6 +121,7 @@
     explicit icuuc icudt icuin ;
 
     ICU_OPTS =   <include>$(ICU_PATH)/include 
+      <cxxflags>-std=c++11
       <library>icuuc/<link>shared/<runtime-link>shared 
       <library>icudt/<link>shared/<runtime-link>shared 
       <library>icuin/<link>shared/<runtime-link>shared
@@ -180,6 +181,7 @@
     explicit icuuc_64 icudt_64 icuin_64 ;
 
     ICU64_OPTS =   <include>$(ICU_PATH)/include 
+      <cxxflags>-std=c++11
       <library>icuuc_64/<link>shared/<runtime-link>shared 
       <library>icudt_64/<link>shared/<runtime-link>shared 
       <library>icuin_64/<link>shared/<runtime-link>shared
--- boost_1_66_0/libs/regex/build/Jamfile.v2.orig	2017-12-13 18:56:48.000000000 -0500
+++ boost_1_66_0/libs/regex/build/Jamfile.v2	2018-04-08 15:20:40.865532505 -0400
@@ -44,7 +44,7 @@
 
    if $(ICU_LINK)
    {
-      ICU_OPTS = <include>$(ICU_PATH)/include <linkflags>$(ICU_LINK) <dll-path>$(ICU_PATH)/bin <define>BOOST_HAS_ICU=1 <runtime-link>shared ;
+      ICU_OPTS = <include>$(ICU_PATH)/include <cxxflags>-std=c++11 <linkflags>$(ICU_LINK) <dll-path>$(ICU_PATH)/bin <define>BOOST_HAS_ICU=1 <runtime-link>shared ;
    }
    else
    {
@@ -78,6 +78,7 @@
 
       ICU_OPTS = 
          <include>$(ICU_PATH)/include 
+         <cxxflags>-std=c++11
          <runtime-link>shared:<library>icuuc/<link>shared
          <runtime-link>shared:<library>icudt/<link>shared
          <runtime-link>shared:<library>icuin/<link>shared
>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/tests/messaging.scm?id=dfcf79ac5943c68dc8013aa333add3f881e894aa&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2018-12-24 11:18:36 +0200'>2018-12-24</span></td><td><a href='/guix/commit/gnu/tests/messaging.scm?id=dcad57d5fca43a111e1b314264171c80d4d9a75b'>services: Add quassel.</a><span class='msg-avail'>...</span></td><td>Efraim Flashner</td></tr>
<tr><td><span title='2018-10-18 01:12:22 +0200'>2018-10-18</span></td><td><a href='/guix/commit/gnu/tests/messaging.scm?id=39d7fdce453b0ca23ecbed72048647debbaa58a6'>services: dhcp-client: Deprecate 'dhcp-client-service' procedure.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2018-06-13 09:11:45 +0200'>2018-06-13</span></td><td><a href='/guix/commit/gnu/tests/messaging.scm?id=c24b15472baaa7ec67d48cbf296bbe5ab727b78f'>tests: Honor the return value of 'start-service'.</a><span class='msg-avail'>...</span></td><td>Clément Lassieur</td></tr>
<tr><td><span title='2018-01-15 23:29:34 +0100'>2018-01-15</span></td><td><a href='/guix/commit/gnu/tests/messaging.scm?id=c1816361ad1390d6bea0fbe8f738c07b966a4605'>services: bitlbee: Add test.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2017-11-26 15:32:16 +0100'>2017-11-26</span></td><td><a href='/guix/commit/gnu/tests/messaging.scm?id=5c22f3726e6a3e44792fd44f7b42122194a16f35'>tests: messaging: Enable Prosody DIGEST-MD5 auth mechanism.</a><span class='msg-avail'>...</span></td><td>Clément Lassieur</td></tr>