create base/fenv.c to standerdize fenv across platforms. It's a c file and not a cpp file because c99

(which defines fenv) doesn't necessarily extend to c++ and it is a problem with solaris. If really
desired this could wrap the ieeefp interface found in bsd* as well, but I see no need at the moment.

src/arch/alpha/isa/fp.isa:
src/arch/sparc/isa/formats/basic.isa:
    use m5_fesetround()/m5_fegetround() istead of fenv interface directly
src/arch/sparc/isa/includes.isa:
    use base/fenv instead of fenv directly
src/base/SConscript:
    add fenv to sconscript
src/base/fenv.hh:
src/base/random.cc:
    m5 implementation to standerdize fenv across platforms.

--HG--
extra : convert_revision : 38d2629affd964dcd1a5ab0db4ac3cb21438e72c

src/base/SConscript

@@ -57,6 +57,7 @@ Source('circlebuf.cc')
 Source('cprintf.cc')
 Source('crc.cc')
 Source('fast_alloc.cc')
+Source('fenv.c')
 Source('fifo_buffer.cc')
 Source('hostinfo.cc')
 Source('hybrid_pred.cc')