Added the -lm library explicitly (closes #44).
Added the -lm library explicitly (closes #44).

andreabedini/numexpr,pombredanne/numexpr,andreabedini/numexpr,pombredanne/numexpr,pydata/numexpr,robbmcleod/numexpr,andreabedini/numexpr,pydata/numexpr,robbmcleod/numexpr,pydata/numexpr,robbmcleod/numexpr,pombredanne/numexpr