This patch adds a check which reports an unsupported value of the maximum_operations_per_instruction field in a debug line table header. This is reported once per line table, at most, and only if the table would otherwise need to use it (i.e. never for tables with version 3 or less, or for tables which don't use DW_LNS_const_add_pc or special opcodes). Unsupported values are currently any apart from 1.
See also D43470, which takes a similar approach for bad line_range values (i.e. 0). I may refactor the pair of them to avoid the code duplication.
Depends on D75188.