Log Message:
glib-networking: Update to 2.60.3

pkgsrc changes:
 - Add options.mk in order to be able to select between `gnutls' and
  `openssl'.  However, no defaults are changed: `openssl' is
   considered experimental by upstream at the moment.
 - Remove dependency to mozilla-rootcerts (default gnutls/openssl
   certificates are now honored instead, should be part of
   Makefile,-r1.41 commit, sorry!)

Changes:
2.60.3
======
 - Fix clobbering of the thread-default main context after certificate
   verification failure during async handshakes since 2.60.1 (#85)
 - Fix GTlsDatabase initialization failures in OpenSSL backend due to
   uninitialized memory use
 - Fix minor leak of ALPN protocols

2.60.2
======
 - OpenSSL backend now defaults to system trust store (#62)
 - Fix client auth failure error with GnuTLS 3.6.7 (#70)