Adds an example in COBOL

[baptistecolin]

Hi, I've added an example of floating point computations in COBOL. The yielded result differes from the usual 0.300...04 because COBOL uses the HFP format for floating point numbers instead of IEEE754, but the same mechanism is at play behind the scenes. When using 64-bits HFP floats, 0.1 + 0.2 actually resolves to 0.3. But 0.1 cannot be correctly represented and resolves to 0.09999999. I thought it was relevant to add it to the example I've tried to keep the code snippest as small as possible, but COBOL isn't really renowned for its conciseness :-) Let me know if you think it deserves any edition Thanks !