[RFE] Support combinations of keys

[ericzolf]

As described at vdr-portal, some keys on my remote MX3 are only sending keys (instead of IR codes) when used in combination with another key, which eventlircd can't interpret:

Event: time 1629495741.496240, type 4 (EV_MSC), code 4 (MSC_SCAN), value 70070
Event: time 1629495741.496240, type 1 (EV_KEY), code 191 (KEY_F21), value 1
Event: time 1629495741.496240, type 4 (EV_MSC), code 4 (MSC_SCAN), value 70075
Event: time 1629495741.496240, type 1 (EV_KEY), code 138 (KEY_HELP), value 1
Event: time 1629495741.496240, -------------- SYN_REPORT ------------
Event: time 1629495741.696218, type 4 (EV_MSC), code 4 (MSC_SCAN), value 70070
Event: time 1629495741.696218, type 1 (EV_KEY), code 191 (KEY_F21), value 0
Event: time 1629495741.696218, type 4 (EV_MSC), code 4 (MSC_SCAN), value 70075
Event: time 1629495741.696218, type 1 (EV_KEY), code 138 (KEY_HELP), value 0
Event: time 1629495741.696218, -------------- SYN_REPORT ------------
Event: time 1629495744.168235, type 4 (EV_MSC), code 4 (MSC_SCAN), value 70070
Event: time 1629495744.168235, type 1 (EV_KEY), code 191 (KEY_F21), value 1
Event: time 1629495744.168235, type 4 (EV_MSC), code 4 (MSC_SCAN), value 70076
Event: time 1629495744.168235, type 1 (EV_KEY), code 130 (KEY_PROPS), value 1
Event: time 1629495744.168235, -------------- SYN_REPORT ------------
Event: time 1629495744.344231, type 4 (EV_MSC), code 4 (MSC_SCAN), value 70070
Event: time 1629495744.344231, type 1 (EV_KEY), code 191 (KEY_F21), value 0
Event: time 1629495744.344231, type 4 (EV_MSC), code 4 (MSC_SCAN), value 70076
Event: time 1629495744.344231, type 1 (EV_KEY), code 130 (KEY_PROPS), value 0
Event: time 1629495744.344231, -------------- SYN_REPORT ------------
Event: time 1629495746.056229, type 4 (EV_MSC), code 4 (MSC_SCAN), value 70070
Event: time 1629495746.056229, type 1 (EV_KEY), code 191 (KEY_F21), value 1
Event: time 1629495746.056229, type 4 (EV_MSC), code 4 (MSC_SCAN), value 70077
Event: time 1629495746.056229, type 1 (EV_KEY), code 132 (KEY_FRONT), value 1
Event: time 1629495746.056229, -------------- SYN_REPORT ------------
Event: time 1629495746.240207, type 4 (EV_MSC), code 4 (MSC_SCAN), value 70070
Event: time 1629495746.240207, type 1 (EV_KEY), code 191 (KEY_F21), value 0
Event: time 1629495746.240207, type 4 (EV_MSC), code 4 (MSC_SCAN), value 70077
Event: time 1629495746.240207, type 1 (EV_KEY), code 132 (KEY_FRONT), value 0
Event: time 1629495746.240207, -------------- SYN_REPORT ------------
Event: time 1629495747.768227, type 4 (EV_MSC), code 4 (MSC_SCAN), value 70070
Event: time 1629495747.768227, type 1 (EV_KEY), code 191 (KEY_F21), value 1
Event: time 1629495747.768227, type 4 (EV_MSC), code 4 (MSC_SCAN), value 70078
Event: time 1629495747.768227, type 1 (EV_KEY), code 128 (KEY_STOP), value 1
Event: time 1629495747.768227, -------------- SYN_REPORT ------------
Event: time 1629495747.960205, type 4 (EV_MSC), code 4 (MSC_SCAN), value 70070
Event: time 1629495747.960205, type 1 (EV_KEY), code 191 (KEY_F21), value 0
Event: time 1629495747.960205, type 4 (EV_MSC), code 4 (MSC_SCAN), value 70078
Event: time 1629495747.960205, type 1 (EV_KEY), code 128 (KEY_STOP), value 0
Event: time 1629495747.960205, -------------- SYN_REPORT ------------