datetime: Fix hashing
datetime: Fix hashing

Convert to the epoch, just like we do when checking for equality, so
that timezones are correctly handled.

https://bugzilla.gnome.org/show_bug.cgi?id=50076

bratsche/glib,bluez-android/glib,ieei/glib,Distrotech/glib,endlessm/glib,pstglia/external-bluetooth-glib,tchakabam/glib,djdeath/glib,pstglia/platform-external-bluetooth-glib,mzabaluev/glib,antono/glib,dicer/android_external_glib,ieei/glib,tamaskenez/glib,darren-clark/android_platform_external_bluetooth_glib,pstglia/platform-external-bluetooth-glib,iConsole/Console-OS_external_bluetooth_glib,pstglia/external-bluetooth-glib,Distrotech/glib,lukasz-skalski/glib,tchakabam/glib,pstglia/platform-external-bluetooth-glib,iConsole/Console-OS_external_bluetooth_glib,MathieuDuponchelle/glib,cosimoc/glib,justinkb/aosp-bluez.glib,bratsche/glib,ahmedammar/platform_external_gst_glib,tchakabam/glib,johne53/MB3Glib,mzabaluev/glib,krichter722/glib,ahmedammar/platform_external_gst_glib,01org/android-bluez-glib,mzabaluev/glib,djdeath/glib,MathieuDuponchelle/glib,cosimoc/glib,pstglia/external-bluetooth-glib,lukasz-skalski/glib,bluez-android/glib,lukasz-skalski/glib,Distrotech/glib,Distrotech/glib,johne53/MB3Glib,djdeath/glib,darren-clark/android_platform_external_bluetooth_glib,lukasz-skalski/glib,ieei/glib-old-android,Distrotech/glib,MathieuDuponchelle/glib,tamaskenez/glib,djdeath/glib,gale320/glib,johne53/MB3Glib,johne53/MB3Glib,bluez-android/glib,01org/android-bluez-glib,endlessm/glib,krichter722/glib,zsx/glib,endlessm/glib,bratsche/glib,cention-sany/glib,dicer/android_external_glib,gale320/glib,justinkb/aosp-bluez.glib,djdeath/glib,ieei/glib,pstglia/external-bluetooth-glib,antono/glib,mzabaluev/glib,ahmedammar/platform_external_gst_glib,cention-sany/glib,johne53/MB3Glib,justinkb/aosp-bluez.glib,zsx/glib,MathieuDuponchelle/glib,iConsole/Console-OS_external_bluetooth_glib,cention-sany/glib,tamaskenez/glib,tchakabam/glib,zsx/glib,justinkb/aosp-bluez.glib,01org/android-bluez-glib,antono/glib,ieei/glib,tamaskenez/glib,ahmedammar/platform_external_gst_glib,gale320/glib,mzabaluev/glib,johne53/MB3Glib,endlessm/glib,01org/android-bluez-glib,dicer/android_external_glib,iConsole/Console-OS_external_bluetooth_glib,pstglia/platform-external-bluetooth-glib,pstglia/external-bluetooth-glib,lukasz-skalski/glib,cosimoc/glib,ieei/glib-old-android,tchakabam/glib,cosimoc/glib,ieei/glib-old-android,bluez-android/glib,gale320/glib,krichter722/glib,zsx/glib,pstglia/platform-external-bluetooth-glib,antono/glib,cention-sany/glib,tamaskenez/glib,cention-sany/glib,darren-clark/android_platform_external_bluetooth_glib,justinkb/aosp-bluez.glib,MathieuDuponchelle/glib,gale320/glib,darren-clark/android_platform_external_bluetooth_glib,bluez-android/glib,bratsche/glib,01org/android-bluez-glib,dicer/android_external_glib,endlessm/glib,cosimoc/glib,iConsole/Console-OS_external_bluetooth_glib,ieei/glib-old-android,dicer/android_external_glib,darren-clark/android_platform_external_bluetooth_glib,ieei/glib,krichter722/glib,krichter722/glib