First go at warning for deprecated symbols.

Added CompilerEnvironment()->PikeCompiler()->{push,pop}_type_attribute().
pike_types_le() now calls the above when encountering asymmetric attribute types.
Added some tests for the above.

Rev: src/pike_compiler.h:1.11
Rev: src/pike_types.c:1.324
Rev: src/program.c:1.686
Rev: src/testsuite.in:1.804