i386: added signed 64bit div/mod helpers in assembly. we have some 64bit heavy code where a direct helper results in about 8-10% of performance advantage compared to going through the generic wrapper + the unsigned function

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@28261 3ad0048d-3df7-0310-abae-a5850022a9f2