[llvm-locstats][NFC] Support OOP concept

Making these changes, the code becomes more robust and easier for
adding the new features.

  -Introduce the LocationStats class representing the statistics
  -Add the pretty_print() method in the LocationStats class
  -Add additional '-' for the program options
  -Add the verify_program_inputs() function
  -Add the parse_locstats() function
  -Rename 'results' => 'opts'
  -Add more comments

Differential Revision: https://reviews.llvm.org/D71868
diff --git a/llvm/docs/CommandGuide/llvm-locstats.rst b/llvm/docs/CommandGuide/llvm-locstats.rst
index 1d05c0c..8fce21d 100644
--- a/llvm/docs/CommandGuide/llvm-locstats.rst
+++ b/llvm/docs/CommandGuide/llvm-locstats.rst
@@ -25,18 +25,18 @@
 OPTIONS
 -------
 
-.. option:: -only-variables
+.. option:: --only-variables
 
-            Calculate the location statistics only for local variables.
+            calculate the location statistics only for local variables
 
-.. option:: -only-formal-parameters
+.. option:: --only-formal-parameters
 
-            Calculate the location statistics only for formal parameters.
+            calculate the location statistics only for formal parameters
 
-.. option:: -ignore-debug-entry-values
+.. option:: --ignore-debug-entry-values
 
-            Ignore the location statistics on locations containing the
-            debug entry values DWARF operation.
+            ignore the location statistics on locations containing the
+            debug entry values DWARF operation
 
 EXIT STATUS
 -----------