Codechange: Replace mishmash of types for widget index with WidgetID.

Indices were stored as int, but often passed around as uint/uint8_t and casts.

Now they should all use WidgetID.

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: C++-ify the Layouter and related functions

They all now access a std::string_view, instead of a "const char *"
or std::string (in some cases).

Additionally, GetCharAtPosition and friends now return an index
instead of a "const char *", as it makes for a more clear interface.

(svn r14514) -Codechange: use 'size' instead of 'length' for querystring and textbuf, explicitly say it includes the terminating zero
-Fix: one couldn't rename things with too long default/automatic name
-Fix: buffer overflow in console when too long (1024 bytes) command was entered