Fix bug pressing warning icon to add palette color when active locale is non-English

It looks like Allegro library was changing the locale to the active
one, and it can break things like strtod() (which is used to convert
colors from string format in AddColor command). In this case, if we added
a HSV color with double floating-point precision, it was added incorrectly
because strtod() wasn't taking the decimal part.

src/allegro/src/x/xkeyboard.c

@@ -697,9 +697,11 @@ static int x_keyboard_init(void)
 
 #ifdef ALLEGRO_XWINDOWS_WITH_XIM
    /* Otherwise we are restricted to ISO-8859-1 characters. */
+/* [dacap] Don't call setlocale()
    if (setlocale(LC_ALL, "") == NULL) {
       TRACE(PREFIX_W "Could not set default locale.\n");
    }
+*/
 
 /* TODO: is this needed?
    modifiers = XSetLocaleModifiers("@im=none");

src/main/main.cpp

@@ -1,5 +1,5 @@
 // Aseprite
-// Copyright (C) 2001-2015  David Capello
+// Copyright (C) 2001-2016  David Capello
 //
 // This program is free software; you can redistribute it and/or modify
 // it under the terms of the GNU General Public License version 2 as
@@ -22,6 +22,7 @@
 #include "she/scoped_handle.h"
 #include "she/system.h"
 
+#include <clocale>
 #include <cstdlib>
 #include <ctime>
 #include <iostream>
@@ -48,8 +49,14 @@ namespace {
 // Aseprite entry point. (Called from she library.)
 int app_main(int argc, char* argv[])
 {
+  // Initialize the locale. Aseprite isn't ready to handle numeric
+  // fields with other locales (e.g. we expect strings like "10.32" be
+  // used in std::strtod(), not something like "10,32").
+  std::setlocale(LC_ALL, "en-US");
+  ASSERT(std::strtod("10.32", nullptr) == 10.32);
+
   // Initialize the random seed.
-  std::srand(static_cast<unsigned int>(std::time(NULL)));
+  std::srand(static_cast<unsigned int>(std::time(nullptr)));
 
 #ifdef _WIN32
   ::CoInitialize(NULL);