Refactor XxxAssignExp semantic

[yebblies]

Reduce code duplication for the semantic routines of +=, -=, *=, /=, %=, &=, |=, ^=, <<=, >>=, >>>=

The semantic routines for these operators are nearly identical, and a lot of the differences are probably bugs.

Most of the remaining special casing is due to imaginary and complex types, which can be delete when those types are removed from the language.

In the process fix issues 7439 and 5181. (and possibly others)

http://d.puremagic.com/issues/show_bug.cgi?id=5181
http://d.puremagic.com/issues/show_bug.cgi?id=7439

[braddr]

doesn't pass testing:
../src/dmd -m32 -Irunnable -odtest_results/runnable -oftest_results/runnable/xtest46_0 runnable/xtest46.d
runnable/xtest46.d(1722): basic type expected, not {
runnable/xtest46.d(1722): found '{' when expecting ')'
runnable/xtest46.d(1723): found 'alias' when expecting ')'
runnable/xtest46.d(1723): { } expected following aggregate declaration

Your new test contains a typo.. did you run it before submitting the pull request? :)

[yebblies]

Heh, nope. (not after the last set of changes) The amazing autotester has made me lazy and careless :) (and more productive).

[Trass3r]

github really should have a voting system for pull requests :)