Implemented plist caching, that gives >30% performance.

--HG--
extra : convert_revision : 6302893f967be96f99a86d499ca62a8c005e56f7

doc/TODO

@@ -41,8 +41,6 @@ xbps-bin:
 
 libxbps:
  * Fix glibc updates: removing libc is bad.
- * When accessing .plist files, only internalize_from_file once to
-   avoid multiple open(3) and fstat(3) calls. [IN PROGRESS]
  * Create xbps_upgrade_pkg() to replace or remove/unpack and register.
    Remove duplicate code from xbps-bin/install.c. [IN PROGRESS]
  * Add support to upgrade packages but overwritting current files;