bug#48775: Making company mode with completion from opened files

[ludvig-faddeev@gmx.com]

Am currently working on a fortran project with company mode for completion.
Although I get emacs specific commands, I would like to get completion on words
for opened files.

If I have an opened file with the following text

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An inverse problem in science is the process of calculating from a set of observations the causal factors that produced them: for example, calculating an image in X-ray computed tomography, source reconstruction in acoustics, or calculating the density of the Earth from measurements of its gravity field. It is called an inverse problem because it starts with the effects and then calculates the causes. It is the inverse of a forward problem, which starts with the causes and then calculates the effects.

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Then if I start writing "tom", company-mode will show me completion with "tomography"