Examples: Use Clang in old Makefile.

examples/opengl2_example/Makefile

@@ -12,6 +12,7 @@
 #
 
 #CXX = g++
+CXX = clang++
 
 EXE = opengl2_example
 OBJS = main.o imgui_impl_glfw_gl2.o

examples/opengl3_example/Makefile

@@ -12,6 +12,7 @@
 #
 
 #CXX = g++
+CXX = clang++
 
 EXE = opengl3_example
 OBJS = main.o imgui_impl_glfw_gl3.o

examples/sdl_opengl3_example/Makefile

@@ -12,6 +12,7 @@
 #
 
 #CXX = g++
+CXX = clang++
 
 EXE = sdl_opengl3_example
 OBJS = main.o imgui_impl_sdl_gl3.o