Codechange: automatic adding of _t to (u)int types, and WChar to char32_t

for i in `find src -type f|grep -v 3rdparty/fmt|grep -v 3rdparty/catch2|grep -v 3rdparty/opengl|grep -v stdafx.h`; do sed 's/uint16& /uint16 \&/g;s/int8\([ >*),;[]\)/int8_t\1/g;s/int16\([ >*),;[]\)/int16_t\1/g;s/int32\([ >*),;[]\)/int32_t\1/g;s/int64\([ >*),;[]\)/int64_t\1/g;s/ uint32(/ uint32_t(/g;s/_uint8_t/_uint8/;s/Uint8_t/Uint8/;s/ft_int64_t/ft_int64/g;s/uint64$/uint64_t/;s/WChar/char32_t/g;s/char32_t char32_t/char32_t WChar/' -i $i; done

Codechange: Remove duplicated includes. (#10888)

These are now included by stdafx.h so don't need to be included again.

Codechange: rename str_validate to StrMakeValid(InPlace) (#9304)

This to be more explicit the function changes the value, and not
returns yes/no.

Add: always set PERSONAL_DIR "/content_download" in search path (#8481)

This means that if you start OpenTTD with "-c" to indicate another
location to store files, it can still read the content you already
downloaded from your PERSONAL_DIR. This folder is, however,
read-only.

This is useful for situations where you downloaded OpenGFX via
the content-service, but want to run the regression or want to
run with a clean configuration. With this change, you no longer
need to download OpenGFX again.

Fix: set SP_WORKING_DIR earlier with '-c'

On Windows, relative folders don't work so well. So we need to
lookup the full path. This is best done in DetermineBasePaths()
and as a bonus that only sets SP_WORKING_DIR once.

Codechange: Replace custom thread code with C++11 thread objects.

We assume a conforming C++11 compiler environment that has a valid <thread>-header.
Failure to run a real thread is handled gracefully.