PrintTo(char8_t) and PrintTo(char16_t) widened their argument to char32_t
and printed it with the U+XXXX notation. That notation names a code point,
but char8_t and char16_t hold code units, so it is wrong for every value
that does not encode a code point on its own: any non-ASCII char8_t (always
part of a multi-unit UTF-8 sequence) and the UTF-16 surrogates D800-DFFF.
For example, PrintTo(char8_t(0x80)) printed "U+0080", the code point of a
character that value cannot represent.
Print those values as code units instead, using the same escape-plus-code
form already used for char, unsigned char and wchar_t: char8_t(0x80) now
prints as u8'\x80' (128) and char16_t(0xD800) as u'\xD800' (55296). Values
that do encode a code point keep the U+XXXX notation.
Fixes#4762
The INSTALL_INTERFACE include directory was written as
$<INSTALL_PREFIX>/${CMAKE_INSTALL_INCLUDEDIR}, which unconditionally
prepends the install prefix. When CMAKE_INSTALL_INCLUDEDIR is an
absolute path, the exported GTestTargets.cmake ends up with an invalid
doubled path such as "/usr/local//usr/local/include", and find_package
consumers fail at configure time with "Imported target includes
non-existent path".
Relative paths inside $<INSTALL_INTERFACE:...> are already interpreted
relative to the installation prefix, so the explicit $<INSTALL_PREFIX>/
prefix is redundant for relative values and wrong for absolute ones.
Dropping it keeps the exported path identical for relative values
(${_IMPORT_PREFIX}/include) and uses absolute values as-is.
Fixes#4817
uditDewan