Libm: all long double math functions are missing

[dplanitzer]

Describe the bug
Libm does not export any of the long double related math functions.

To Reproduce
Write code that uses some long double functions like sqrtl(), compile and link the code.

Expected behavior
Compiles, links and runs just fine.

OS (please complete the following information):

• Version 0.7.0-alpha

[dplanitzer]

This is a known problem.

We're currently building libm with VBCC. VBCC doesn't support C99 hex floating point constants. The code for long double functions heavily uses this kind of constants. It's not practical to change all those constants to decimal constants because this would introduce a ton of changes compared to the original Openlibm code and thus incorporating bug fixes and other code changes into our libm version would becomes much more work and error prone.