LDC 1.5.0-beta1

[Guillaume Piolat]

Some measurements for some audio processing. Output are identical 
across compilers (30 measures).


### LDC 1.2.0

Results:
  * minimum time: 440 ms => 48.024 x real-time
  * median  time: 443 ms => 47.6987 x real-time
  * average time: 444.233 ms => 47.5663 x real-time

### LDC 1.3.0

Results:
  * minimum time: 439 ms => 48.1334 x real-time
  * median  time: 442 ms => 47.8067 x real-time
  * average time: 442.6 ms => 47.7419 x real-time

### LDC 1.4.0

Results:
  * minimum time: 436 ms => 48.4646 x real-time
  * median  time: 439 ms => 48.1334 x real-time
  * average time: 439.767 ms => 48.0494 x real-time


### LDC 1.5.0-b1

Results:
  * minimum time: 429 ms => 49.2553 x real-time
  * median  time: 432 ms => 48.9133 x real-time
  * average time: 433.3 ms => 48.7665 x real-time


Results are only precise up to the ~0.5% range.

So approx. +2.5% relative improvement in LDC 1.5.0-b1 vs LDC 1.2, 
free lunch is always good.

The number of flags in -help-hidden seems very large, I haven't 
tried any yet (apart from -enable-unsafe-fp-math which seems to 
lose speed like -ffast-math, for this benchmark).