perl: Set gccversion configuration symbol correctly

This was previously manually set to '4.8.0'. Aside from just being incorrect,
it also breaks Errno's GCC5 detection.

Fixes #2044.

Signed-off-by: Marcel Denia <naoir@gmx.net>

lang/perl/files/README.config

@@ -45,6 +45,7 @@ owrt:threads          yes/no              Whether to enable threading support.
 owrt:ipv6             define/undef        Whether to enable IPv6 support.
 owrt:target_cross     *                   Target architecture's host triplet.
 owrt:target_cc        *                   C compiler to use.
+owrt:gccversion       *                   target_cc's version number.
 owrt:cflags           *                   Additional C compiler flags.
 owrt:ldflags          *                   Additional linker flags.
 owrt:staging_dir      *                   Same as OpenWRT buildroot's

lang/perl/files/misc.config

@@ -1,6 +1,6 @@
 cf_email='naoir@gmx.net'
 osvers='3.18.19'
-gccversion='4.8.0'
+gccversion="$owrt:gccversion"
 myhostname='OpenWrt'
 cf_time='Thu Jan 1 12:00:00 CEST 2015'