+ added rtl/i8086/mathu*.inc for compiling the math unit

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@24595 3ad0048d-3df7-0310-abae-a5850022a9f2
* do not use fsin and fcos on 286-, since they're 387+

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@24596 3ad0048d-3df7-0310-abae-a5850022a9f2
+ enabled compilation of the math unit for i8086-msdos

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@24597 3ad0048d-3df7-0310-abae-a5850022a9f2
+ enabled compilation of unit macpas for i8086-msdos

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@24598 3ad0048d-3df7-0310-abae-a5850022a9f2