Floating point support for audio post processing components

Source code is added/modified to support floating point processing for
audio post processing components.All the changes are done under the macro
BUILD_FLOAT

Enable/disable this macro in Android.mk files to build floating point or
fixed point code.

Based on the macro either fixed point code or floating point code gets compiled.

By default this macro is ENABLED.

(cherry picked from partner commit 2ceaff6aafadbcb0fb6d5135ca814ba7c790ab1a)
(Minor merge conflicts solved, some formatting and safety changes,
bugfixes in EffectReverb.cpp)

Test: audio comparisons between integer and floating point effects

Change-Id: Idb044ace1e8da1d86c67667aba0101ae8da6788e