Made OpenSSL not mandatory. Don't build examples if OpenSSL is not found.

Spdylay library itself does not depend on OpenSSL. The example programs
in examples directory do. Spdylay library should be built without
OpenSSL.

configure.ac

@@ -88,7 +88,16 @@ fi
 AM_CONDITIONAL([HAVE_CUNIT], [ test "x${have_cunit}" = "xyes" ])
 
 # openssl (for examples)
-PKG_CHECK_MODULES([OPENSSL], [openssl >= 1.0.1])
+PKG_CHECK_MODULES([OPENSSL], [openssl >= 1.0.1],
+                  [have_openssl=yes], [have_openssl=no])
+if test "x${have_openssl}" = "xno"; then
+  AC_MSG_NOTICE($OPENSSL_PKG_ERRORS)
+  AC_MSG_NOTICE([The example programs will not be built.])
+fi
+
+# The example programs depend on OpenSSL
+enable_examples=$have_openssl
+AM_CONDITIONAL([ENABLE_EXAMPLES], [ test "x${enable_examples}" = "xyes" ])
 
 # Checks for header files.
 AC_CHECK_HEADERS([ \
@@ -152,4 +161,6 @@ AC_MSG_NOTICE([summary of build options:
     CFlags:         ${CFLAGS}
     Library types:  Shared=${enable_shared}, Static=${enable_static}
     CUnit:          ${have_cunit}
+    OpenSSL:        ${have_openssl}
+    Examples:       ${enable_examples}
 ])

examples/Makefile.am

@@ -21,6 +21,8 @@
 # OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
 # WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
+if ENABLE_EXAMPLES
+
 AM_CFLAGS = -Wall
 AM_CPPFLAGS = -Wall -I$(srcdir)/../lib/includes -I$(builddir)/../lib/includes \
 	@OPENSSL_CFLAGS@ @DEFS@
@@ -63,3 +65,5 @@ spdynative_SOURCES = ${HELPER_OBJECTS} ${HELPER_HFILES} \
 	${SPDY_SERVER_OBJECTS} ${SPDY_SERVER_HFILES} \
 	spdy.h spdynative.cc
 endif # HAVE_STDCXX_11
+
+endif # ENABLE_EXAMPLES

tests/Makefile.am

@@ -40,6 +40,12 @@ main_LDFLAGS = -static @CUNIT_LIBS@
 AM_CFLAGS = -Wall -g -O2 -I${top_srcdir}/lib -I${top_srcdir}/lib/includes -I${top_builddir}/lib/includes \
 	@CUNIT_CFLAGS@ @DEFS@
 
-TESTS = main end_to_end.py
+TESTS = main
+
+if ENABLE_EXAMPLES
+
+TESTS += end_to_end.py
+
+endif # ENABLE_EXAMPLES
 
 endif # HAVE_CUNIT