Merge LLDB plugin into master

Summary:
LLDB plugin is now working for basic debugging use cases.

Things that work:

• Basic execution control: start, continue, step etc.
• Break points
• Frame stack list
• Symbol info when hover
• Variables & Expressions (still have caveats)
• Multi-threaded debugee (must use LLDB trunk version)
• Debugger console
• Remote debugging (only tested on localhost)

Things not working yet:

• Disassembly/Register view
• Memory view
• Pending break points and anything requires pending break points
• Watch points
• Attach to process (works internally, no UI to access it)

Not tested:

• Examine core file
• Drkonqi support

There's a debugers/lldb/TODO.txt which contains more detailed description of current limitations and link to related LLDB bug reports.

Note: the whole thing might crash from time to time without this bug fixed. I'm using LLDB built myself with the code fixed. The patch can be found in the bug report.

Test Plan:

• GDB unit tests (such that I didn't break anything)
• LLDB unit tests (some of them are skipped due to limitations mentioned above)
• Manually tested

Reviewers: apol, KDevelop

Reviewed By: apol, KDevelop

Subscribers: kdevelop-devel

Differential Revision: https://phabricator.kde.org/D2293