Volt's gas pedal only and combined gas/acc (commaai#76)

Some messages can't be used for 'user gas' as they
reflect ACC gas/regen commands too.

gm_global_a_powertrain.dbc

@@ -145,7 +145,8 @@ BO_ 189 EBCMRegenPaddle: 7 K17_EBCM
  SG_ RegenPaddle : 7|4@0+ (1,0) [0|0] ""  NEO
 
 BO_ 190 ECMAcceleratorPos: 6 K20_ECM
- SG_ AcceleratorPos : 23|8@0+ (1,0) [0|0] ""  NEO
+ SG_ BrakePedalPos : 15|8@0+ (1,0) [0|0] "sticky"  NEO
+ SG_ GasPedalAndAcc : 23|8@0+ (1,0) [0|0] ""  NEO
 
 BO_ 715 ASCMGasRegenCmd: 8 K124_ASCM
  SG_ GasRegenAlwaysOne2 : 9|1@0+ (1,1) [1|1] ""  NEO
@@ -173,6 +174,15 @@ BO_ 711 BECMBatteryVoltageCurrent: 6 K17_EBCM
  SG_ HVBatteryVoltage : 31|12@0+ (0.125,0) [0|511.875] "V"  NEO
  SG_ HVBatteryCurrent : 12|13@0- (0.15,0) [-614.4|614.25] "A"  NEO
 
+BO_ 417 AcceleratorPedal: 8 XXX
+ SG_ AcceleratorPedal : 55|8@0+ (1,0) [0|0] ""  NEO
+
+BO_ 451 GasAndAcc: 8 XXX
+ SG_ GasPedalAndAcc2 : 55|8@0+ (1,0) [0|0] ""  NEO
+
+BO_ 452 AcceleratorPedal2: 8 XXX
+ SG_ AcceleratorPedal2 : 47|8@0+ (1,0) [0|0] ""  NEO
+
 BO_TX_BU_ 384 : K124_ASCM,NEO;
 BO_TX_BU_ 880 : NEO,K124_ASCM;
 BO_TX_BU_ 1033 : K124_ASCM,NEO;
@@ -189,6 +199,8 @@ CM_ BU_ K114B_HPCM "Hybrid Powertrain Control Module";
 CM_ BU_ NEO "Comma NEO";
 CM_ BU_ K124_ASCM "Active Safety Control Module";
 CM_ SG_ 381 MSG17D_AccPower "Need to investigate";
+CM_ SG_ 190 GasPedalAndAcc "ACC baseline is 62";
+CM_ SG_ 451 GasPedalAndAcc2 "ACC baseline is 62";
 BA_DEF_  "UseGMParameterIDs" INT 0 0;
 BA_DEF_  "ProtocolType" STRING ;
 BA_DEF_  "BusType" STRING ;