signal emission: Allocate instance_and_param with alloca
signal emission: Allocate instance_and_param with alloca

This Gives a 5% performance increase in e.g. the emit-handled test.

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