Lang: don't panic if more arguments are past to an function than expected

[aequitas]

Given the following mcl:

$x = getenv("TEST", "321")

This change will turn this:

00:28:50 lang.go:126: lang: Running Type Unification...
panic: runtime error: index out of range

goroutine 161 [running]:
github.com/purpleidea/mgmt/lang/unification.SimpleInvariantSolver(0xc4202f0780, 0x1e, 0x28, 0xc42052f970, 0xc4202e3300, 0xc42016e550, 0xc4202f0780)
	/Users/johan/.gopath/src/github.com/purpleidea/mgmt/lang/unification/simplesolver.go:356 +0x770c
github.com/purpleidea/mgmt/lang/unification.SimpleInvariantSolverLogger.func1(0xc4202f0780, 0x1e, 0x28, 0x28, 0x0, 0x0)
	/Users/johan/.gopath/src/github.com/purpleidea/mgmt/lang/unification/simplesolver.go:40 +0x48
github.com/purpleidea/mgmt/lang/unification.Unify(0x5ef8840, 0xc42032a6a0, 0xc42052f980, 0x1, 0x1)
	/Users/johan/.gopath/src/github.com/purpleidea/mgmt/lang/unification/unification.go:51 +0x8f
github.com/purpleidea/mgmt/lang.(*Lang).Init(0xc4202aa3f0, 0xc4202aa3f0, 0x207)
	/Users/johan/.gopath/src/github.com/purpleidea/mgmt/lang/lang.go:127 +0x6e0
github.com/purpleidea/mgmt/lang.(*GAPI).LangInit(0xc4202be880, 0x0, 0x0)
	/Users/johan/.gopath/src/github.com/purpleidea/mgmt/lang/gapi.go:142 +0x1f4
github.com/purpleidea/mgmt/lang.(*GAPI).Next.func1(0xc4202be880, 0xc420264300)
	/Users/johan/.gopath/src/github.com/purpleidea/mgmt/lang/gapi.go:220 +0x4af
created by github.com/purpleidea/mgmt/lang.(*GAPI).Next
	/Users/johan/.gopath/src/github.com/purpleidea/mgmt/lang/gapi.go:176 +0x8b

Into this:

00:28:13 lang.go:126: lang: Running Type Unification...
...
00:28:16 etcd.go:798: Etcd: Exiting callback loop!
00:28:16 etcd.go:960: Etcd: Exiting loop!
00:28:16 main.go:841: Main: Error: can't init the lang: could not unify types: func arg count differs
00:28:16 main.go:843: Goodbye!
00:28:16 cli.go:168: Main: Error: can't init the lang: could not unify types: func arg count differs

[purpleidea]

Confirmed!

[purpleidea]

Still reviewing the patch, but examples/lang/env* should be updated to not have this incorrect version in it.

[aequitas]

@purpleidea the commit is in another castle PR #361 8ed6043

[purpleidea]

Fixed in ff69a82

Thanks for the great report!