* compiler: -g and -debug should always add -g at least in the C compiler by default.
* Set first the C backend debug_options, so that the optimization_options can override them later.
* Implement cleaner named is_debug, is_vlines, is_keep_c and is_cache options (i.e. -g/-cg, -keep_c, -cache v flags).
* Check and reset file/line numbers in the generated main program, only if v.pref.is_vlines is true.
* Add source line numbers to backtraces on linux.
* Fix -g (broken after token caching).
* reset the #line directives after all the v code is compiled
* cleanup p.cgen.line setting inside p.next() .
* Support windows filepaths like "C:\Users\travis\build\vlang\v\v.exe.tmp.c" inside generated #line directives.
* Try to diagnose better windows-gcc failing.
* Revert "Try to diagnose better windows-gcc failing."
* implement and use cescaped_path/1 .
* Use cescaped_path/1 consistently throughout compiler/ .
* compiler: streamline C main function generation
* fix most tests
* compiler: fix for 'go update()' in graph.v . More precise parser error messages.
* Fix temporarily examples/hot_reload/message.v by using os inside it (os.clear).
* Make graph.v easier to quickly modify by defining y outside the loop.
* Fix failure of /v/nv/compiler/tests/defer_test.v when run with 'v -g' (#line directive was not on its own line, but right after } ).
* Do not pass the os.args to tests, even if the tests import os (they are more stable when run in a controlled environment).
* fix declared and not used in the js backend.
* fix js main => main__main too.
