comp.el: Minor improvements

comp.el: Minor improvements

Change: (comp-start-async-worker) Refactor slightly

Change: (comp-start-async-worker) Inline (comp-to-file-p)

Change: (comp-source-files) Rename from comp-src-pool

Add: (comp-start-async-worker) Assertion

Change: (comp-async-processes) Rename from comp-prc-pool

Tidy: (native-compile)

Rename variables, improve docstring, adjust log message, simplify
filename code.

Tidy: (batch-native-compile) Docstring

Tidy: whitespace-cleanup

Tidy: (comp-start-async-worker) Use () instead of nil

Tidy: (comp-files-queue) Rename from comp-source-files

Change: (native-compile-async) Improve paths support

Tidy: Comment

Save a line for one word.  :)

Change: (comp-log) Rewrite without macro, follow tail

Change: (native-compile-async) Use end-of-string in filename regexps

Change: (native-compile-async) Use cl-loop instead of dotimes

Add/Change: (comp-log-to-buffer) And use in comp-log

Comment: Tidy comment

Fix: (configure.ac) Option description

Fix: (comp-log) Argument

Fix: (comp-start-async-worker) Variable name

Change: Undo whitespace changes

Some of them included incorrect indentation because the
macros' (declare (indent)) forms were not loaded.  The
whitespace-cleanup should be run from Emacs 27+ with the file loaded.