Support hex numbers that start with a letter (a-f)
When entering numbers like 'ce' some ambiguity arises because this could be interpreted as 'light speed times euler's number' or as '0xce'. To resolve this decide based on wheter the calculator is in Numeral System mode or not.
(cherry picked from commit 17933a6e)
Co-authored-by: Gabriel Barrantes gabriel.barrantes.dev@outlook.com