[MERGED] bring in advantages from branch to trunk; Performance optimizations

This combines now the changes from branch PerformanceOptimizations to trunk
Mainly this change should do following:
- Flash savings should be around 224 bytes for stock
- Added option ARITHMETIC_OVERFLOW_CHECK to prevent overflows.
  Still not bulletproof, but codecost is about 50 bytes
- Increases mix speed about 25 - 30% depending on task for stock
  Also increased for other boards, but they may not notice...
- Increased ranges for weight and offset from +-125% to +-245%
- Easier now to increase number of GVARS if needed; Just increase GVAR_MAX in myeeprom.h.
  But!!!! EEPROM layout changes and may not be compatible. Do this for own proposes.
  Till now we do not know how we handle this in future.
- Corrected Timer for stock if used together with AUDIO or VOICE option
- See comments below, what I potentially forgotten...

Be aware this version is currently not compatible to companion9x. But the version before wasn't either. Work is current in progress to tie this up.

src/Makefile

@@ -97,6 +97,14 @@ AUDIO = NO
 # Values = YES, NO 
 VOICE = NO
 
+# corrects different rounding for negative values. So instead of -99.9 you will see again -100.0
+# Values = YES, NO
+CORRECT_NEGATIVE_VALUES = YES
+
+# adds additional code to prevent arithmetic overflows. MAX or MIN values stays. Not yet guaranteed!! Just improved
+# Values = YES, NO
+ARITHMETIC_OVERFLOW_CHECK = NO
+
 # HAPTIC Mods
 # Values = YES, NO 
 HAPTIC = NO
@@ -423,6 +431,14 @@ ifeq ($(GVARS), YES)
   EEPROM_VARIANT += ${GVARS_VARIANT}
 endif
 
+ifeq ($(CORRECT_NEGATIVE_VALUES), YES)
+  CPPDEFS += -DCORRECT_NEGATIVE_SHIFTS
+endif
+
+ifeq ($(ARITHMETIC_OVERFLOW_CHECK), YES)
+  CPPDEFS += -DPREVENT_ARITHMETIC_OVERFLOW
+endif
+
 # If STD-Support is enabled
 ifeq ($(EXT), STD)
   CPPDEFS += -DEXTSTD