* RTL: fixed some warnings when compiling for x86_64:
  * x86_64/x86_64.inc: IsMultithread is a LongBool, not Boolean -> fixed assembler instruction suffixes
  * inc/generic.inc: cast Sizeof() to unsigned, so that combining it with unsigned operands does not cause promotion to larger signed type.
  + win64/seh64.inc: explicit typecast and missing function result assignment.
  + inc/genmath.inc: explicit typecasts.


git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@25384 3ad0048d-3df7-0310-abae-a5850022a9f2