Remove calls to impure mathlib functions.
Make std.string.indexOf @safe
Mark std.string.indexOf as @safe
Replace trusted lambda block with trusted nested function
Implement pure floor()/ceil().
Implement pure tan().
Implement pure atan().
Implement pure atan2().
Implement pure exp().
Implement pure expm1().
Implement pure exp2().
Implement pure log().
Implement pure log10().
Implement pure log1p().
Implement pure log2().
Implement pure lrint().
Implement pure pow().
Fixup std.math unittests for new math implementations.
Add cast to Char*
Mark std.string.splitLines as @safe pure