Add x86 support

[tony--]

I'm a developer working on the Intel HTML5 Tools team and a Cordova committer.
I noticed that this plugin includes an Android native library, but currently only includes support for arm:

src/android/armeabi/libnmsp_speex.so

As it stands, this plugin should work on x86 devices thanks to libhoudini, but there is some power and performance cost to pay for this magic 🎩. In order to deliver the best performance and lowest power consumption, plugins with native libraries need to include an x86 version of the native library. This article describes how to compile libraries for x86 and includes a section on how to build speex for x86.