Add "operator bool" to SB APIs

Summary:
Our python version of the SB API has (the python equivalent of)
operator bool, but the C++ version doesn't.

This is because our python operators are added by modify-python-lldb.py,
which performs postprocessing on the swig-generated interface files.

In this patch, I add the "operator bool" to all SB classes which have an
IsValid method (which is the same logic used by modify-python-lldb.py).
This way, we make the two interfaces more constent, and it allows us to
rely on swig's automatic syntesis of python __nonzero__ methods instead
of doing manual fixups.

Reviewers: zturner, jingham, clayborg, jfb, serge-sans-paille

Subscribers: jdoerfert, lldb-commits

Differential Revision: https://reviews.llvm.org/D58792

llvm-svn: 355824

lldb/source/API/SBPlatform.cpp

@@ -287,6 +287,10 @@ SBPlatform::~SBPlatform() {}
 
 bool SBPlatform::IsValid() const {
   LLDB_RECORD_METHOD_CONST_NO_ARGS(bool, SBPlatform, IsValid);
+  return this->operator bool();
+}
+SBPlatform::operator bool() const {
+  LLDB_RECORD_METHOD_CONST_NO_ARGS(bool, SBPlatform, operator bool);
 
   return m_opaque_sp.get() != NULL;
 }