Refactor diag of unresolved syms; also diagnose in getAddressOfGlobal().

(cherry picked from commit 562befca35097083d3959ba7fb42aa5a4f3c91be)
Bring back old diag format.

(cherry picked from commit 65005add8390bae686aeb61e7ed3cab71fb8187e)
Accessor to "is file opened"; this is crucial info for us.

(cherry picked from commit c2b0b00532c9116e1ff95552783c28c479a4f5ad)
Show parsed (with open file handle?) versus deserialized.

(cherry picked from commit 73ae682cd38dfd05eac577bfe316b37f7a40482b)
Fix doc warning.

(cherry picked from commit 862d79d1f83ad6778c6dce8ce9e8f9129b5ff59c)
Fix doxygen warning.

(cherry picked from commit d1311307426576ff562a3f8855e4655bc6cdbb88)
Hide all llvm, clang, cling includes behind a facade.

(cherry picked from commit 6d1fed7a9c36c4f0410440e88b198c793284e7c3)
Return 0 to signal missing symbols.

(cherry picked from commit 0e60925635b0399e9423cbff8a46932813c487d5)
Be explicit about what failed to "compile" (now that we know).

(cherry picked from commit 9fc39e60c4e297828ecbd27d239ccf09dcf4bd46)