Add isWithinTransaction()

[HarryMuc]

Documents isWithinTransaction(), which Lucee (since 5.3.9.4) and BoxLang provide to detect whether code runs inside a cftransaction block. It returns true as soon as the block is entered, even before the first query runs.

Adobe ColdFusion has no documented equivalent, so there is no coldfusion engine entry. The function is also added to the index files and to the related lists of cftransaction and the transaction* functions.

The schema allows only three version parts, so the Lucee minimum_version is 5.3.9 with the exact version (5.3.9.4) in the notes.

[HarryMuc]

Both foundeo/cfdocs#1743 and foundeo/cfdocs#1744 are updated against current master. Heads-up: they both touch the single-line function lists, so whichever you merge second will conflict again — just ping me and I'll rebase it.