Set SOVERSION in CMake shared library builds.

And correct SO_VERSION_MAJOR in libs.mk.

BUG=aomedia:627

Change-Id: Ia0a3bb5774fa44c182e4f8072ffe90970ee2aeb5

CMakeLists.txt

@@ -401,6 +401,7 @@ endif ()
 if (BUILD_SHARED_LIBS)
   include("${AOM_ROOT}/build/cmake/exports.cmake")
   setup_exports_target()
+  set_target_properties(aom PROPERTIES SOVERSION 0)
 endif ()
 
 # Aomedia documentation rule.

libs.mk

@@ -196,7 +196,7 @@ OBJS-yes += $(LIBAOM_OBJS)
 LIBS-$(if yes,$(CONFIG_STATIC)) += $(BUILD_PFX)libaom.a $(BUILD_PFX)libaom_g.a
 $(BUILD_PFX)libaom_g.a: $(LIBAOM_OBJS)
 
-SO_VERSION_MAJOR := 3
+SO_VERSION_MAJOR := 0
 SO_VERSION_MINOR := 0
 SO_VERSION_PATCH := 0
 ifeq ($(filter darwin%,$(TGT_OS)),$(TGT_OS))