[lldb][NFC] Add documentation for SBFrame::GetRegisters

SBFrame::GetRegisters() (and the .registers / .regs extensions in
Python) returns an array of register-set's, not registers like you
might expect from the API name.  Document this.

Author: jasonmolenda

lldb/bindings/interface/SBFrameDocstrings.i

@@ -78,6 +78,22 @@ See also SBThread."
     See also GetFunctionName()."
 ) lldb::SBFrame::IsInlined;
 
+%feature("docstring", "
+    Returns an SBValueList which is an array of one or more register
+    sets that exist for this thread.  
+    Each SBValue in the SBValueList represents one register-set. 
+    The first register-set will be the general purpose registers -- 
+    the registers printed by the `register read` command-line lldb, with 
+    no additional arguments.  
+    The register-set SBValue will have a name, e.g. 
+    SBFrame::GetRegisters().GetValueAtIndex(0).GetName() 
+    may be 'General Purpose Registers', but the general purpose 
+    register-set may not use that exact name, it is only a convention 
+    used by some stubs.
+    A register-set SBValue will have children, one child per register 
+    in the register-set."
+) lldb::SBFrame::GetRegisters;
+
 %feature("docstring", "
     Return true if this frame is artificial (e.g a frame synthesized to
     capture a tail call). Local variables may not be available in an artificial

lldb/bindings/interface/SBFrameExtensions.i

@@ -87,8 +87,8 @@ STRING_EXTENSION_OUTSIDE(SBFrame)
         args = property(get_arguments, None, doc='''A read only property that returns a list() that contains a collection of lldb.SBValue objects that represent the argument variables in this stack frame.''')
         arguments = property(get_arguments, None, doc='''A read only property that returns a list() that contains a collection of lldb.SBValue objects that represent the argument variables in this stack frame.''')
         statics = property(get_statics, None, doc='''A read only property that returns a list() that contains a collection of lldb.SBValue objects that represent the static variables in this stack frame.''')
-        registers = property(GetRegisters, None, doc='''A read only property that returns a list() that contains a collection of lldb.SBValue objects that represent the CPU registers for this stack frame.''')
-        regs = property(GetRegisters, None, doc='''A read only property that returns a list() that contains a collection of lldb.SBValue objects that represent the CPU registers for this stack frame.''')
+        registers = property(GetRegisters, None, doc='''A read only property that returns a list() of register sets for this thread.  See SBFrame::GetRegisters() for details.''')
+        regs = property(GetRegisters, None, doc='''A read only property that returns a list() of register sets for this thread.  See SBFrame::GetRegisters() for details.''')
         register = property(get_registers_access, None, doc='''A read only property that returns an helper object providing a flattened indexable view of the CPU registers for this stack frame.''')
         reg = property(get_registers_access, None, doc='''A read only property that returns an helper object providing a flattened indexable view of the CPU registers for this stack frame''')
         parent = property(get_parent_frame, None, doc='''A read only property that returns the parent (caller) frame of the current frame.''')