[boost] [modularization] Extracting lexical_cast from conversion

Conversion depends on Math and Range due to lexical_cast. /math/ http://www.pdimov.com/tmp/report-6d1f271/math.html || * from || || * from || /range/ http://www.pdimov.com/tmp/report-6d1f271/range.html || * from || |Extracting LexicalCast  allows to break these cycle|s Conversion -> Math -> Conversion -> Range -> Conversion Best, Vicente P.S. This dependencies have been introduced lately while trying to make the implementation more efficient.