Fix out-of-bounds read in ChemistryStr

- Check BATTERY_INFORMATION Chemistry[4] for null terminator.

Chemistry is a string that is "not necessarily zero-terminated".

Prior to this change ChemistryStr() did not check for null and
incorrectly used sizeof to get the read size of parameter
UCHAR Chemistry[4] which decays to UCHAR *Chemistry.

For 32-bit builds ChemistryStr happened to work by luck, though it may
have read the null into std::string. MS currently uses only strings of
length 3 or 4, and the size of *Chemistry is 4 so ChemistryStr never
read past 4 bytes. For example {'N','i','Z','n'} or {'R','A','M','\0'}.

For 64-bit builds the pointer size is 8 and it read at least 4 bytes too
many.

Ref: https://docs.microsoft.com/en-us/windows/win32/power/battery-information-str

battstatus.cpp

@@ -309,7 +309,13 @@ string TechnologyStr(UCHAR Technology)
 
 string ChemistryStr(const UCHAR Chemistry[4])
 {
-  return string((char *)Chemistry, sizeof Chemistry);
+  /* Chemistry is "not necessarily zero-terminated" */
+  int i;
+  for(i = 0; i < 4; ++i) {
+    if(Chemistry[i] == '\0')
+      break;
+  }
+  return string((const char *)Chemistry, i);
 }
 
 string DesignedCapacityStr(ULONG DesignedCapacity,