Minor adjusts (#1001)

* contributing: Use should instead of thould

* interpreter: Use exist_ok parameter in subdir function

We explicitly depend on python 3.4 or newer, which means the exist_ok
parameter is available. Use it instead of a try with a pass on except.

* authors: Add my name at the end of authors file

authors.txt

@@ -54,3 +54,4 @@ Alexandre Foley
 Jouni Kosonen
 Aurelien Jarno
 Mark Schulte
+Paulo Antonio Alvarez

contributing.txt

@@ -32,7 +32,7 @@ those are simple.
 External dependencies
 
 The goal of Meson is to be as easily usable as possible. The user
-experience thould be "get Python3 and Ninja, run", even on
+experience should be "get Python3 and Ninja, run", even on
 Windows. Unfortunately this means that we can't have dependencies on
 projects outside of Python's standard library. This applies only to
 core functionality, though. For additional helper programs etc the use

mesonbuild/interpreter.py

@@ -2177,10 +2177,7 @@ requirements use the version keyword argument instead.''')
                                    % subdir)
         self.visited_subdirs[subdir] = True
         self.subdir = subdir
-        try:
-            os.makedirs(os.path.join(self.environment.build_dir, subdir))
-        except FileExistsError:
-            pass
+        os.makedirs(os.path.join(self.environment.build_dir, subdir), exist_ok=True)
         buildfilename = os.path.join(self.subdir, environment.build_filename)
         self.build_def_files.append(buildfilename)
         absname = os.path.join(self.environment.get_source_dir(), buildfilename)