[patch] Allow ford=stepping_stones with intermittent=yes

[Famlam]

What steps will reproduce the problem?

1. Validate ​https://www.openstreetmap.org/way/948851674
2. Intermittent without waterway, natural=water|spring, landuse=basin|reservoir or ford=yes

What is the expected result?

No warning, also fords with stepping stones can be intermittent

What happens instead?

Validator warning

Please provide any additional information below. Attach a screenshot if possible.

https://josm.openstreetmap.de/browser/josm/trunk/resources/data/validator/combinations.mapcss#L230

*[intermittent                 ][!waterway][natural!~/^(water|spring)$/][landuse!~/^(basin|reservoir)$/][ford!=yes],
*[boat                         ][!waterway][natural!=water             ][landuse!~/^(basin|reservoir)$/][ford!=yes] {
  throwWarning: tr("{0} without {1}, {2}, {3} or {4}", "{0.key}", "{1.key}", "{2.tag}", "{3.tag}", "{4.tag}");
  group: tr("missing tag");
}

could become

*[intermittent][!waterway][natural!~/^(water|spring)$/][landuse!~/^(basin|reservoir)$/][ford!~/^(yes|stepping_stones)$/],
*[boat        ][!waterway][natural!=water             ][landuse!~/^(basin|reservoir)$/][ford!=yes] {
  throwWarning: tr("{0} without {1}, {2}, {3} or {4}", "{0.key}", "{1.key}", "{2.tag}", "{3.tag}", "{4.tag}");
  group: tr("missing tag");
}

(I didn't include it in the second one as I guess it's unlikely that a boat can pass through stepping stones)

URL:https://josm.openstreetmap.de/svn/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2021-04-27 20:35:33 +0200 (Tue, 27 Apr 2021)
Build-Date:2021-04-27 21:58:39
Revision:17833
Relative:URL: ^/trunk

Identification: JOSM/1.5 (17833 nl) Windows 10 64-Bit
OS Build number: Windows 10 Home 2009 (19042)
Memory Usage: 653 MB / 1820 MB (546 MB allocated, but free)
Java version: 1.8.0_291-b10, Oracle Corporation, Java HotSpot(TM) 64-Bit Server VM
Look and Feel: com.sun.java.swing.plaf.windows.WindowsLookAndFeel
Screen: \Display0 1920×1080 (scaling 1.00×1.00)
Maximum Screen Size: 1920×1080
Best cursor sizes: 16×16→32×32, 32×32→32×32
System property file.encoding: Cp1252
System property sun.jnu.encoding: Cp1252
Locale info: nl_NL
Numbers with default locale: 1234567890 -> 1234567890
Dataset consistency test: No problems found

Plugins:
+ OpeningHoursEditor (35640)
+ SimplifyArea (35640)
+ imagery_offset_db (35640)
+ pt_assistant (2.1.6)
+ reverter (35732)
+ tageditor (35640)
+ turnlanes-tagging (288)
+ undelete (35640)
+ utilsplugin2 (35691)

Map paint styles:
- https://josm.openstreetmap.de/josmfile?page=Styles/Lane_and_Road_Attributes&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/PublicTransport&zip=1
+ %UserProfile%\Documents\tijdelijke bestanden\josm-eigen.mappaint.mapcss
- https://josm.openstreetmap.de/josmfile?page=Styles/Sidewalks&zip=1

Validator rules:
+ %UserProfile%\Documents\tijdelijke bestanden\josm-eigen.validator.mapcss

[Klumbumbus]

In 17923/josm:

fix #20942 - Don't warn about intermittent=yes on ford=stepping_stones (patch by Famlam)