Add some whitespace to signature files.

Floating-point update.

• isSignallingNan predicate is added to machine_ieeeTheory.
• The RISC-V model is simplified in places (for DIV and REM).
• The L3 import is extended to cover more operations.

Minor changes within floating-point theory.

• The operations float_negate1985 and float_abs1985 have been removed.
• Added a predicate float_is_signalling and renamed float_some_nan to float_some_qnan.
• Fixed problem with EQ_tm and GT_tm being swapped in binary_ieeeSyntax.

Update for latest L3.

Removes some unnecessary bracketing.

Update RISC-V SML code.

Should have been included with commit 4b08982.

Add SML version of RISC-V model.