Move Compilation::PrintJob and PrintDiagnosticJob into Job::Print.

This moves the code to Job.cpp, which seems like a more natural fit,
and replaces the "is this a JobList? is this a Command?" logic with
a virtual function call.

It also removes the code duplication between PrintJob and
PrintDiagnosticJob and simplifies the code a little.

There's no functionality change here, except that the Executable is
now always printed within quotes, whereas it would previously not be
quoted in crash reports, which I think was a bug.

Differential Revision: http://llvm-reviews.chandlerc.com/D1653

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@190620 91177308-0d34-0410-b5e6-96231b3b80d8
Move the execution code from Compilation::ExecuteCommand to Command::Execute

I think it makes sense that a Command knows how to execute itself.

There's no functionality change but i rewrote the code to avoid the manual
memory management of Argv.

My motivation for this is that I plan to subclass Command to build fall-back
functionality into clang-cl.

Differential Revision: http://llvm-reviews.chandlerc.com/D1654

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@190621 91177308-0d34-0410-b5e6-96231b3b80d8
PR16054: Slight strengthening for -Wsometimes-uninitialized: if we use a
variable uninitialized every time we reach its (reachable) declaration, or
every time we call the surrounding function, promote the warning from
-Wmaybe-uninitialized to -Wsometimes-uninitialized.

This is still slightly weaker than desired: we should, in general, warn
if a use is uninitialized the first time it is evaluated.


git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@190623 91177308-0d34-0410-b5e6-96231b3b80d8