MIPS, improved integer to real conversions:
* Use fpc_[int64|qword]_to_double instead of [int64|qword]_to_float64, makes RTL no longer dependent on softfloat code.
* Move 32-bit values from integer registers to FPU registers without using memory.
* Fixed branching, was still using a macro and delay slot was missing.

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@25071 3ad0048d-3df7-0310-abae-a5850022a9f2