There was only one function in module ipc: eintr_retry_call. This
function was used in pdftohtml module, and turns out[1] it's not needed
anymore. Support for retrying on syscall interrupts was introduced in
Python 3.5 (which was released in 2015), and covers subprocess module
among other modules. In this commit, mentioned eintr_retry_call function
has been removed, and couple of cosmetic changes was done in module
pdftohtml.
[1] https://www.python.org/dev/peps/pep-0475/
This is progressing refactor of the calibre code to make it more
readable, and transform it to something more coherent.
In this patch, there are changes regarding imports for some modules,
instead of polluting namespace of each module with some other modules
symbols, which often were imported from other modules. Yuck.
