Make the emoji version configurable.

Makefile.am

@@ -55,7 +55,7 @@ EXTRA_DIST += ChangeLog
 
 ############################# Unicode Data ####################################
 
-EMOJI_VERSION=5.0
+EMOJI_VERSION=@EMOJI_VERSION@
 UCD_VERSION=@UCD_VERSION@
 UCD_ROOTDIR=data/ucd
 UCD_SRCDIR=http://www.unicode.org/Public

configure.ac

@@ -41,6 +41,14 @@ AC_ARG_WITH([unicode-version],
 
 AC_SUBST(UCD_VERSION)
 
+AC_ARG_WITH([emoji-version],
+    [AS_HELP_STRING([--with-emoji-version], [Unicode emoji version to support @<:@default=5.0@:>@])],
+    [AS_IF([test x"$withval" != x],
+           [EMOJI_VERSION="$withval"])],
+    [EMOJI_VERSION="5.0"])
+
+AC_SUBST(EMOJI_VERSION)
+
 dnl ================================================================
 dnl Compiler warnings.
 dnl
@@ -70,4 +78,5 @@ AC_MSG_NOTICE([
         C++ Compiler flags:            ${CXXFLAGS}
 
         Unicode version:               ${UCD_VERSION}
+        Emoji version:                 ${EMOJI_VERSION}
 ])