Modiffied toolchains to use absolute paths for each tool to avoid paths like path/to/../../path/to/toolchain/../../gcc

retargeted __enable_irq and __disable_irq, mbed_die

Improvements for porting to PC (TDM GCC compieler)

Successful port for PC: first test was compiled and executed as EXE on my PC

TODO: tollchains do not support EXE generation - this needs to be added so in mbed sdk 2.0 we can actually link to EXE (not to ELF etc.)