Upgrade Android build to Gradle build system

The old Ant build system has been deprecated for a while and new development is focused on Gradle.
I also removed a hardcoded string that lint caught and moved the patch files to a subdirectory.
I left the JNI files in the root directory.

build/android/patches/libvorbis-libogg-fpu.patch

@@ -0,0 +1,37 @@
+--- libvorbis-libogg-android/jni/libvorbis-jni/Android.mk.orig	2014-06-17 19:22:50.621559073 +0200
++++ libvorbis-libogg-android/jni/libvorbis-jni/Android.mk	2014-06-17 19:38:20.641581140 +0200
+@@ -4,9 +4,6 @@
+ 
+ LOCAL_MODULE := vorbis-jni
+ LOCAL_CFLAGS += -I$(LOCAL_PATH)/../include -fsigned-char
+-ifeq ($(TARGET_ARCH),arm)
+-	LOCAL_CFLAGS += -march=armv6 -marm -mfloat-abi=softfp -mfpu=vfp
+-endif
+ 
+ LOCAL_SHARED_LIBRARIES := libogg libvorbis
+ 
+--- libvorbis-libogg-android/jni/libvorbis/Android.mk.orig	2014-06-17 19:22:39.077558797 +0200
++++ libvorbis-libogg-android/jni/libvorbis/Android.mk	2014-06-17 19:38:52.121581887 +0200
+@@ -4,9 +4,6 @@
+ 
+ LOCAL_MODULE := libvorbis
+ LOCAL_CFLAGS += -I$(LOCAL_PATH)/../include -ffast-math -fsigned-char
+-ifeq ($(TARGET_ARCH),arm)
+-	LOCAL_CFLAGS += -march=armv6 -marm -mfloat-abi=softfp -mfpu=vfp
+-endif
+ LOCAL_SHARED_LIBRARIES := libogg
+ 
+ LOCAL_SRC_FILES := \
+--- libvorbis-libogg-android/jni/libogg/Android.mk.orig	2014-06-17 19:22:33.965558675 +0200
++++ libvorbis-libogg-android/jni/libogg/Android.mk	2014-06-17 19:38:25.337581252 +0200
+@@ -4,10 +4,6 @@
+ 
+ LOCAL_MODULE := libogg
+ LOCAL_CFLAGS += -I$(LOCAL_PATH)/../include -ffast-math -fsigned-char
+-ifeq ($(TARGET_ARCH),arm)
+-	LOCAL_CFLAGS += -march=armv6 -marm -mfloat-abi=softfp -mfpu=vfp
+-endif
+-
+ 
+ LOCAL_SRC_FILES := \
+ 	bitwise.c \