Stop automatic syntax tests missing gaps (#398)

[camila314]

Fixes #398
Old Version (incorrectly assumes the space has numerical scopes):

    (123 456)
/*  ^^^^^^^^^ meta.group.c-2 */
/*  ^ punctuation.section.group.begin */
/*   ^^^^^^^ meta.number.integer.decimal.c-2 constant.numeric.value.c-2 */
/*          ^ punctuation.section.group.end */```

New Version (correctly excludes space from numerical scopes):

    (123 456)
/*  ^^^^^^^^^ meta.group.c-2 */
/*  ^ punctuation.section.group.begin */
/*   ^^^ meta.number.integer.decimal.c-2 constant.numeric.value.c-2 */
/*       ^^^ meta.number.integer.decimal.c-2 constant.numeric.value.c-2 */
/*          ^ punctuation.section.group.end */

Simply checks if the previous region's end matches with the new region's beginning when inserting into a ScopeTreeNode.

[michaelblyons]

I also recommend adding "Fixes #398” to the OP body text, since GitHub recognizes certain specific patterns as formal links between an issue and a PR.

Also consider changing the title to something like "Fix automatic syntax assertions filling gaps" or "Stop automatic syntax tests missing gaps". I think the way it is now it sounds backwards to me.

[FichteFoll]

Thanks for taking a look at this issue and fixing it.