configure: Add missing --enable-examples option, mentioned in docs

The `examples/` directory was never built.  The documentation however
indicated the existence of an `--enable-examples` option, which didn't
really exist.  This patch adds that option.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

Makefile.am

@@ -4,6 +4,10 @@ DIST_SUBDIRS        = src examples tests
 doc_DATA            = API.md README.md LICENSE
 EXTRA_DIST          = API.md README.md LICENSE AUTHORS ChangeLog.md
 
+if ENABLE_EXAMPLES
+SUBDIRS            += examples
+endif
+
 ## Generate .deb package
 package:
 	@dpkg-buildpackage -uc -us -B

configure.ac

@@ -11,4 +11,10 @@ AC_PROG_CC
 AM_PROG_AR
 LT_INIT
 
+# Optional features
+AC_ARG_ENABLE([examples],
+	[AC_HELP_STRING([--enable-examples], [Build libuEv examples/ directory])],
+	[], [enable_examples=no])
+AM_CONDITIONAL([ENABLE_EXAMPLES], [test "$enable_examples" = yes])
+
 AC_OUTPUT