Merge pull request #73 from ladislav/dtoa

Use David M. Gay's dtoa for molding decimals - this is a major change to decimal handling that makes Rebol more compatible over a wider range of C libraries and CPUs.
Merge pull request #74 from earl/fix-select-series

Fix value returned by SELECT with a series argument
Fix recursive make calls

Instead of hardcoding the name of the make command, use the predefined
$(MAKE) variable for recursive make invocations.

This fixes the build for environments where make is called something
else (like `gmake`, or `mingw32-make`). $(MAKE) is standardised in
POSIX's make specification and present in at least GNU make and BSD
make.

Problem most recently brought to attention by Adrian Sampaleanu.