The getMachODefaultTextSection and getMachODefaultRWDataSection functions
return the "__TEXT,__text" and "__DATA,__data" sections respectively, creating
empty sections if the default sections are not already present in the graph.
These functions can be used by utilities that want to add code or data to these
standard sections (e.g. these functions can be used to supply the section
argument to the createAnonymousPointerJumpStub and
createPointerJumpStubBlock functions in the various targets).
