Compiler crashes if there's an error in a PETSCII escape code

[mrg-75]

If you enter an unrecognised PETSCII escape sequence, the compiler throws an error.

Example:

print "{abc}"

std.conv.ConvException@C:\hostedtoolcache\windows\dc\dmd-2.090.1\x64\dmd2\windows\bin\..\..\src\phobos\std\conv.d(2312): Unexpected 'a' when converting from type string to type uint

[JJFlash-IT]

This also happens if you enter a valid PETSCII escape sequence, but not in upper case, like {clr} or {CLr} instead of {CLR}