NuttX build and run simple hello world

[seanshpark]

NuttX build with current iotjs, run simple hello world script.

• include jerry math lib
  • Improve target flags handling #51
  • Add jerry fdlibm library in build script #52 > drop
  • Generate jerry third-party math library for embed systems #55
• fix "out of memory" problem
  • grow jerry heap size: jerryscript-project/jerryscript@a28d03a
  • Question about mem_stats jerryscript#103 (Issue, Question about mem_stats)
  • API for expanding Magic string jerryscript#109 (Issue, API for expanding Magic string)
  • Byte code snap-shot to save runtime heap jerryscript#111 (Issue, Byte code snap-shot to save runtime heap)
  • New External Magic String API to save heap memory jerryscript#136 (PR, New External Magic String API to save heap memory)
  • register magic strings of iotjs
• prepare very simple test script

console.log("Hello IoT.js");

[ILyoan]

I think this can be close now.
Feel free to reopen if needed.