Fix spelling errors

aligment -> alignment
purgable -> purgeable
thead -> thread

src/alloc-override-osx.c

@@ -201,7 +201,7 @@ static void __attribute__((constructor)) _mi_macosx_override_malloc()
   zone.pressure_relief = &zone_pressure_relief;
   intro.zone_locked = &intro_zone_locked;
 
-  // force the purgable zone to exist to avoid strange bugs
+  // force the purgeable zone to exist to avoid strange bugs
   if (malloc_default_purgeable_zone) {
     purgeable_zone = malloc_default_purgeable_zone();
   }

src/alloc-override-win.c

@@ -34,7 +34,7 @@ by us is freed after we unpatched.
 
 There are two tricky situations to deal with:
 
-1. The Thread Local Storage (TLS): when the main thead stops it will call registered
+1. The Thread Local Storage (TLS): when the main thread stops it will call registered
    callbacks on TLS entries (allocated by `FlsAlloc`). This is done by the OS
    before any DLL's are unloaded. Unfortunately, the C runtime registers such
    TLS entries with CRT allocated memory which is freed in the callback.

src/page-queue.c

@@ -18,13 +18,13 @@ terms of the MIT license. A copy of the license can be found in the file
 ----------------------------------------------------------- */
 
 #if (MI_MAX_ALIGN_SIZE > 4*MI_INTPTR_SIZE)
-  #error "define aligment for more than 4x word size for this platform"
+  #error "define alignment for more than 4x word size for this platform"
 #elif (MI_MAX_ALIGN_SIZE > 2*MI_INTPTR_SIZE)
   #define MI_ALIGN4W   // 4 machine words minimal alignment
 #elif (MI_MAX_ALIGN_SIZE > MI_INTPTR_SIZE)
   #define MI_ALIGN2W   // 2 machine words minimal alignment
 #else
-  // ok, default aligment is 1 word
+  // ok, default alignment is 1 word
 #endif