"slice" of shared string returns invalid result

cmake Toolchain improvement (Target x86, mips, AVR32, ARM, etc.)

Add first sample for MIPS cross compile

add auxiliary data pointer to mrb_state

memory leak in kh_resize_##name()

Use value.i for nil/false check.

Add Ubuntu -> Linux-on-ARM sample CMake toolchain files

Add separate sample CMake toolchain files targeting Linux running
on ARM, with and without hardware floating point support. Samples
use the `gcc-arm-linux-gnueabihf` and `gcc-arm-linux-gnueabi` cross
toolchains from the standard Ubuntu package repositories.

Added Math.sqrt() that was missing in math.c, and added relevant test case

Merge branch 'jf/parser-dump' of https://github.com/thecodeshop/mruby into thecodeshop-jf/parser-dump

Improve Time