Add arith instruction assemble and disassemble support
support of ldw/ldb/stw/stb
add ldw reg, label support and .word relocation
Add testsuite support for UniCore32 gas
Add testcase of arith instruction

$ make check-gas
or
$ cd gas && make-check
to run this testcase
Testcase for ldw/ldb/stw/stb
Testcase for "ldw Label" syntax
Support of register alias name. (pc, lr, fp etc)
Testcase for register alias name
extract ld/st suffix-processing code
format fix
Support stm instruction