Add "try/catch" expression encapsulating any expression

[Chuck]

x = int.parse(input) catch FormatError get 0

See full discussion at  Shortcut syntax idea for catch.

[Chuck]

Per the discussion, the syntax should start with the try keyword:

x = try int.parse(input) catch FormatError get 0

Also, there are implementation hints in the discussion.

[Chuck]

Changing from defect to enhancement.

[hopscc]

Implements simplified case - trycatch expression as target of assignment statement.

Use in any other expression or statement generate compiler error

tryExpr0.cobra(6): error: Can only use a tryCatch expression as the simple target of an assignment (e.g "ID = try EXPR catch EXCEPTION get EXPR". More complicated expressions cannot have code generated without side effects.

[hopscc]

Second patch implements full support in any expression( on .Net).
Java version still constrained to simple assignment expressions
pending closures in Java

Tests extended somewhat from first patch.

[Charles]

bump

[Charles]

looking now

[Charles]

Nicely done.

Patched applied in changeset:2690