Add __NDK_FPABI__ to function taking/returning float/double

Allow user code to be compiled with "-mhard-float" for armeabi-v7a
(which implies -mfloat-abi=hard), and either link with
1. Android native APIs which use softfp, or
2. A customized libm_hard.a which is compiled with -mhard-float. Need
   -D_NDK_MATH_NO_SOFTFP=1

See tests/device/hard-float/jni/Android.mk for details and restriction
on Clang

Change-Id: I773a842c73368e08b9a6cda0441e95a96fa303b2
20 files changed