Stage 3 of clang compiler warning patches. Replace deprecated 'isa' c…

[ethoms]

…alls.

Stage 3: CAUTION
These fix deprecated 'isa' calls by using object_getClass and object_setClass. This may cause problem with older compilers/objc libraries.

[buzzdeee]

Tested this, together with the others up to stage8 of the clang fixes on:
OpenBSD -current

• amd64, clang-3.5, libobjc2-1.8
• i386, clang-3.5, libobjc2-1.8
• macppc, gcc-4.2.1, libobjc2-1.8
  No issues so far, besides my comment on the stage8 fix

[extrafu]

This will break Ubuntu Lucid builds. GNUstep under Lucid does not provide the Objective2 bundle so object_getClass is undefined.

Lucid LTS reached EOL - I guess it's time for us to drop it.

[ethoms]

OK, I thought RHEL 5.11 was the oldest supported runtime to test against. If you want, I'll try to come up with a solution. I could add some #if statements to check for lack of Objective2 and then #define a substitution back to 'isa'. Just let me know if that's necessary.