aarch32-rt v0.3.0

• el2-mode feature, to keep CPU in EL2 mode
• Discard entry for .ARM.exidx and .ARM.extab sections
• Region alignment support, with _region_alignment linker symbol
• __sXXX and __eXXX linker symbols for each output section
• Support for setting up stacks for multiple cores
• Support for exception handling at EL2 (including a new HypervisorCall handler)
• .pushsection and .popsection to all assembly blocks to avoid accidentally changing the section of another piece of code
• New sections module for getting information about linker output sections at run-time