[e-lang] Bug (0.9.1b): old when syntax fails with "not a poser"

[Kevin Reid]

? e`when (a) -> a(b) {}`
# problem: Failed: Internal: not a poser: [epatt`a`]
#
#   - static EParser#valueMaker(Twine)
#   . <makeEParser>.valueMaker("when (a) -> a(b) {}")
#   @ valueMaker/1
#   - EExpr#evalToPair(Scope)
#   . e`e__quasiParser.valueMaker(...ubstitute(__makeList.run()) 
`.evalToPair(<a Scope>)
#   @ evalToPair/1: <jar:file:/Stuff/e/e.jar!/org/erights/e/elang/cmd/ 
cmdMakerMaker.emaker#:span::124:57::124:66>

While this syntax is deprecated, the parser shouldn't be failing with  
a cryptic error giving no source position.

-- 
Kevin Reid                            <http://homepage.mac.com/kpreid/>