Add blurb for PowerPC.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_33@183500 91177308-0d34-0410-b5e6-96231b3b80d8
Updated the links in the LLDB 3.3 sub-project (now 3.3 links) to fix the 3.4 merge from trunk.
- Also split out a section on build portability and updated the list of features and improvements.
--- This now reflects the up-coming merge of patches from trunk into the release_33 branch.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_33@183554 91177308-0d34-0410-b5e6-96231b3b80d8