various glyphs missing alignment zones

Following a user report from @kaibernau, I surveyed the glyphs of Source Code for near-misses of vertical metrics or alignment zones. Here is the result:

```
SourceCode-ExtraLight.ufo
=========================
2 above 722 (ascender zone): dhook, esh, tesh, schwa.sups
2 below 722 (ascender zone): litre
1 above 660 (cap height): J, W, Z, OE – no functional effect, but I guess it’s a question of “neatness”

SourceCode-Upright.ufo
======================
2 above 712 (ascender zone): esh, schwa.sups
1 above 656 (cap height): W

SourceCode-Black.ufo
====================
2 above 708 (ascender zone): slash, backslash (could be deliberate)
2 below 696 (ascender zone): Yat, eighthnote
2 below 650 (cap height): at
1 below -12 (baseline zone): circledotted

SourceCode-ExtraLightItalic.ufo
===============================
1 above 722 (ascender): dtail
1 above 490 (x-height zone): ereversed
2 below -12 (baseline overshoot): zero.cap, zero.0c,

SourceCode-Italic.ufo
=====================
1 above 668 (cap overshoot): Dhook
1 above 656: (cap height) W, Bstroke
1 above 498 (x-height zone): ereversed

SourceCode-BlackItalic.ufo
==========================
2 above 708 (ascender overshoot): slash, backslash, diamond, spade (could be deliberate)
2 below 696 (ascender): eighthnote
1 above 662 (cap zone): Dhook, Schwa, at.case, florin, Omega.math, lozenge, house
1 above 650 (cap height): W, X, Y, Z, Bstroke, Delta.math
1 below 650 (cap height): dong
1 above 646 (figure zone): perthousand
2 above 592 (osf zone): zero.onum, zero.0o
1 below 580 (osf height): five.onum, seven.onum
1 above 500 (x-height): hsmall
1 above 0 (baseline): hsmall
1 below -12 (baseline overshoot): perthousand, onetenth, circledotted
```

Many of those don’t really matter because the alignment zones will do their thing – I’ll leave it up to you if you have the time to fix those or not :-)