Merge pull request #843 from qtxie/float-datatype

Float datatype
TESTS: lexer float literals tests added.
FEAT: improved and fixed compiler's lexer for float literals.
Merge branch 'float' of github.com:red/red into float
FEAT: allow simple quotes to be used among fractional part of floats.
FEAT: added float support to runtime lexer.
TESTS: added LOAD float tests.
Merge pull request #850 from qtxie/float-datatype

FEAT: added TO action for integer and float.
FEAT: added an accurate string-to-float function.