Some ARM vmov similar to 'vmov.f32 s1, s2' will incorrectly have the second
register added to the symbol table by the assembler. On further
investigation it was found the problem was with the my_get_expression
function. This is called by parse_big_immediate.

Fix this by moving the call to parse_big_immediate to the end of the if,
else if, ..., else block.
Add support for the vmsr and vmrs instructions. This supports the system
level version of the instructions. When used in userland the hardware only
allows us to read/write FPSCR.