build: require c++11 for gtest, and link test exe against pthreads (linux build fails without it)

Makefile

@@ -4,7 +4,16 @@ GTEST := gtest-1.7.0
 
 LDFLAGS=-O2 -Wall -Werror -fPIC
 CFLAGS=-O2 -Wall -Werror -fPIC -I. -Wno-unused-function
-GTEST_CFLAGS=-I$(GTEST)/include
+ifneq (,$(findstring gcc, $(CC)))
+	# gcc's maybe-unintialized is too imprecise, disable it.
+	# clang disbles this functionality by default and doesn't recognize the flag.
+	# (check for CC that contains rather than equals 'gcc',
+	#  to accommodate using specific versions, like gcc-4.9 etc)
+	CFLAGS += -Wno-maybe-uninitialized
+endif
+
+GTEST_CFLAGS=-I$(GTEST)/include -std=c++11
+GTEST_LDFLAGS=-lpthread
 
 all: capn.so capnpc-c test
 
@@ -30,4 +39,4 @@ gtest-all.o: $(GTEST)/src/*.cc
 	$(CXX) -g -Wall -Werror -I. $(GTEST_CFLAGS) -I$(GTEST) -o $@ -c $<
 
 capn-test: capn-test.o capn-stream-test.o compiler/test.capnp.o compiler/schema-test.o compiler/schema.capnp.o gtest-all.o
-	$(CXX) -g -Wall -Werror -I. -o $@ $^
+	$(CXX) -g -Wall -Werror -I. $^ $(GTEST_LDFLAGS) -o $@