Add dlclose to prevent memory leak

A dynamically allocated pointer was not being properly cleaned up.

This fixes the following Coverity issue:
```
lib/pkg_editor/src/zlib.c:119:1:
  Type: Resource leak (RESOURCE_LEAK)

lib/pkg_editor/src/zlib.c:98:3:
  1. path: Condition "zlib_interface.deflateInit_", taking false branch.
lib/pkg_editor/src/zlib.c:101:3:
  2. alloc_fn: Storage is returned from allocation function "zlib_load_library".
lib/pkg_editor/src/zlib.c:90:3:
  2.1. path: Condition "dlopen_handle", taking false branch.
lib/pkg_editor/src/zlib.c:93:3:
  2.2. alloc_fn: Storage is returned from allocation function "dlopen".
lib/pkg_editor/src/zlib.c:93:3:
  2.3. return_alloc_fn: Directly returning storage allocated by "dlopen".
lib/pkg_editor/src/zlib.c:101:3:
  3. var_assign: Assigning: "library" = storage returned from "zlib_load_library()".
lib/pkg_editor/src/zlib.c:102:3:
  4. path: Condition "library == NULL", taking false branch.
lib/pkg_editor/src/zlib.c:110:3:
  5. noescape: Resource "library" is not freed or pointed-to in "load_one_symbol".
lib/pkg_editor/src/zlib.c:39:36:
  5.1. noescape: "load_one_symbol(void *, char const *)" does not free or save its parameter "library".
lib/pkg_editor/src/zlib.c:111:3:
  6. noescape: Resource "library" is not freed or pointed-to in "load_one_symbol".
lib/pkg_editor/src/zlib.c:39:36:
  6.1. noescape: "load_one_symbol(void *, char const *)" does not free or save its parameter "library".
lib/pkg_editor/src/zlib.c:112:3:
  7. noescape: Resource "library" is not freed or pointed-to in "load_one_symbol".
lib/pkg_editor/src/zlib.c:39:36:
  7.1. noescape: "load_one_symbol(void *, char const *)" does not free or save its parameter "library".
lib/pkg_editor/src/zlib.c:113:3:
  8. noescape: Resource "library" is not freed or pointed-to in "load_one_symbol".
lib/pkg_editor/src/zlib.c:39:36:
  8.1. noescape: "load_one_symbol(void *, char const *)" does not free or save its parameter "library".
lib/pkg_editor/src/zlib.c:114:3:
  9. noescape: Resource "library" is not freed or pointed-to in "load_one_symbol".
lib/pkg_editor/src/zlib.c:39:36:
  9.1. noescape: "load_one_symbol(void *, char const *)" does not free or save its parameter "library".
lib/pkg_editor/src/zlib.c:115:3:
  10. noescape: Resource "library" is not freed or pointed-to in "load_one_symbol".
lib/pkg_editor/src/zlib.c:39:36:
  10.1. noescape: "load_one_symbol(void *, char const *)" does not free or save its parameter "library".
lib/pkg_editor/src/zlib.c:119:1:
  11. leaked_storage: Variable "library" going out of scope leaks the storage it points to.
```

Author: IlanTruanovsky

lib/pkg_editor/src/zlib.c

@@ -116,6 +116,11 @@ static void zlib_load() {
 #ifdef _MSC_VER
 #pragma warning(pop)
 #endif
+#ifdef _WIN32
+  FreeLibrary(library)
+#else
+  dlclose(library);
+#endif
 }
 
 int zlib_deflateInit(z_streamp strm, int level) {