POSIX: fix man page links

C<> inside the L<> causes the links to be interpreted as module links rather than the intended links to manpages.

Author: Grinnz

ext/POSIX/lib/POSIX.pod

@@ -1132,7 +1132,7 @@ Not implemented.  C<malloc()> is C-specific.  Perl does memory management transp
 
 This is the same as the C function C<mblen()> on unthreaded perls.  On
 threaded perls, it transparently (almost) substitutes the more
-thread-safe L<C<mbrlen>(3)>, if available, instead of C<mblen>.
+thread-safe C<L<mbrlen(3)>>, if available, instead of C<mblen>.
 
 Core Perl does not have any support for wide and multibyte locales,
 except Unicode UTF-8 locales.  This function, in conjunction with
@@ -1161,7 +1161,7 @@ actual length of the first parameter string.
 
 This is the same as the C function C<mbtowc()> on unthreaded perls.  On
 threaded perls, it transparently (almost) substitutes the more
-thread-safe L<C<mbrtowc>(3)>, if available, instead of C<mbtowc>.
+thread-safe C<L<mbrtowc(3)>>, if available, instead of C<mbtowc>.
 
 Core Perl does not have any support for wide and multibyte locales,
 except Unicode UTF-8 locales.  This function, in conjunction with