Made httplib_pthread_getspecific global

doc/api/httplib_pthread_getspecific.md

@@ -0,0 +1,26 @@
+# LibHTTP API Reference
+
+### `httplib_pthread_getspecific( key );`
+
+### Parameters
+
+| Parameter | Type | Description |
+| :--- | :--- | :--- |
+|**`key`**|`pthread_key_t`|The key of the variable to retrieve|
+
+### Return Value
+
+| Type | Description |
+| :--- | :--- |
+|`void *`|Pointer to the memory area or NULL of no area could be found|
+
+### Description
+
+The platform independent function `httplib_pthread_getspecific()` is used to retrieve a memory area for a thread registered previously with a call to [`httplib_pthread_setspecific()`](httplib_pthread_setspecific.md). If no area could be found, the value `NULL` is returned instead. On systems which support it, the functionality is implemented as a direct call to `pthread_setspecific()`. On other systems own code is used to emulate the same behaviour.
+
+### See Also
+
+* [`httplib_pthread_key_create();`](httplib_pthread_key_create.md)
+* [`httplib_pthread_key_delete();`](httplib_pthread_key_delete.md)
+* [`httplib_pthread_self();`](httplib_pthread_self.md)
+* [`httplib_pthread_setspecific();`](httplib_pthread_setspecific.md)