Merge .hgignore from "master" branch to "legacy".
Streamline the build system infrastructure.
Correct improper naming of assembly language source files.

--HG--
rename : mingwrt/mingwex/math/ceilf.S => mingwrt/mingwex/math/ceilf.s
rename : mingwrt/mingwex/math/ceill.S => mingwrt/mingwex/math/ceill.s
rename : mingwrt/mingwex/math/copysign.S => mingwrt/mingwex/math/copysign.s
rename : mingwrt/mingwex/math/copysignf.S => mingwrt/mingwex/math/copysignf.s
rename : mingwrt/mingwex/math/copysignl.S => mingwrt/mingwex/math/copysignl.s
rename : mingwrt/mingwex/math/cosf.S => mingwrt/mingwex/math/cosf.s
rename : mingwrt/mingwex/math/cosl.S => mingwrt/mingwex/math/cosl.s
rename : mingwrt/mingwex/math/exp2.S => mingwrt/mingwex/math/exp2.s
rename : mingwrt/mingwex/math/exp2f.S => mingwrt/mingwex/math/exp2f.s
rename : mingwrt/mingwex/math/exp2l.S => mingwrt/mingwex/math/exp2l.s
rename : mingwrt/mingwex/math/floorf.S => mingwrt/mingwex/math/floorf.s
rename : mingwrt/mingwex/math/floorl.S => mingwrt/mingwex/math/floorl.s
rename : mingwrt/mingwex/math/fma.S => mingwrt/mingwex/math/fma.s
rename : mingwrt/mingwex/math/fmaf.S => mingwrt/mingwex/math/fmaf.s
rename : mingwrt/mingwex/math/frexpl.S => mingwrt/mingwex/math/frexpl.s
rename : mingwrt/mingwex/math/ilogb.S => mingwrt/mingwex/math/ilogb.s
rename : mingwrt/mingwex/math/ilogbf.S => mingwrt/mingwex/math/ilogbf.s
rename : mingwrt/mingwex/math/ilogbl.S => mingwrt/mingwex/math/ilogbl.s
rename : mingwrt/mingwex/math/log10f.S => mingwrt/mingwex/math/log10f.s
rename : mingwrt/mingwex/math/log10l.S => mingwrt/mingwex/math/log10l.s
rename : mingwrt/mingwex/math/log1p.S => mingwrt/mingwex/math/log1p.s
rename : mingwrt/mingwex/math/log1pf.S => mingwrt/mingwex/math/log1pf.s
rename : mingwrt/mingwex/math/log1pl.S => mingwrt/mingwex/math/log1pl.s
rename : mingwrt/mingwex/math/log2.S => mingwrt/mingwex/math/log2.s
rename : mingwrt/mingwex/math/log2f.S => mingwrt/mingwex/math/log2f.s
rename : mingwrt/mingwex/math/log2l.S => mingwrt/mingwex/math/log2l.s
rename : mingwrt/mingwex/math/logf.S => mingwrt/mingwex/math/logf.s
rename : mingwrt/mingwex/math/logl.S => mingwrt/mingwex/math/logl.s
rename : mingwrt/mingwex/math/nearbyint.S => mingwrt/mingwex/math/nearbyint.s
rename : mingwrt/mingwex/math/nearbyintf.S => mingwrt/mingwex/math/nearbyintf.s
rename : mingwrt/mingwex/math/nearbyintl.S => mingwrt/mingwex/math/nearbyintl.s
rename : mingwrt/mingwex/math/remainder.S => mingwrt/mingwex/math/remainder.s
rename : mingwrt/mingwex/math/remainderf.S => mingwrt/mingwex/math/remainderf.s
rename : mingwrt/mingwex/math/remainderl.S => mingwrt/mingwex/math/remainderl.s
rename : mingwrt/mingwex/math/remquo.S => mingwrt/mingwex/math/remquo.s
rename : mingwrt/mingwex/math/remquof.S => mingwrt/mingwex/math/remquof.s
rename : mingwrt/mingwex/math/remquol.S => mingwrt/mingwex/math/remquol.s
rename : mingwrt/mingwex/math/scalbn.S => mingwrt/mingwex/math/scalbn.s
rename : mingwrt/mingwex/math/scalbnf.S => mingwrt/mingwex/math/scalbnf.s
rename : mingwrt/mingwex/math/scalbnl.S => mingwrt/mingwex/math/scalbnl.s
rename : mingwrt/mingwex/math/sinf.S => mingwrt/mingwex/math/sinf.s
rename : mingwrt/mingwex/math/sinl.S => mingwrt/mingwex/math/sinl.s
rename : mingwrt/mingwex/math/tanf.S => mingwrt/mingwex/math/tanf.s
rename : mingwrt/mingwex/math/tanl.S => mingwrt/mingwex/math/tanl.s