A suspended translation unit uses significantly less memory but on the other
side does not support any other calls than clang_reparseTranslationUnit to
resume it or clang_disposeTranslationUnit to dispose it completely.
This helps IDEs to reduce the memory footprint. The data that is freed
by a call to clang_suspendTranslationUnit will be re-generated on the
next (re)parse anyway. Used with a preamble, this allows pretty fast
resumption of the translation unit for further use (compared to disposal of
the translation unit and a parse from scratch).