I have never head of \l and MSVC warns about unknown escape sequence, so
I changed it into \f that definitely exists and potentially might be
useful.

1. If escape char is first char, sets start of range
2. Multiple escape chars are handled (offsets chars to remove)

Changed default main to clamp exit code to 8 bits because of POSIX limitations.

Updated documentation about declaring non-default main.

This prevents Clang from complaining about unused value in expressions
containing explicit casts used in the THROW assertion macro family.

Example:
`REQUIRE_THROWS_AS(static_cast<bool>(object), std::bad_cast);` would
trigger `-Wunused-value` warning. Now it does not.

Credits to Arto Bendiken, who submitted a PR almost 3 years ago, but his
branch has since died and I was unable to merge it.

The integrated assembler segment was missing an underscore:
"_asm__". Also we remove the "DEBUG" macro check, so we are consistent
with the linux and windows variant.
Now breaking into gdb on failure should work via:
	gdb --args test_executable --break

Should fix #796

Using sizeof(expr) can trigger a compile-time error,
"lambda expressions are not allowed in an unevaluated context", when passing
expression containing lambda, like a std algorithm. This error is considered
a standard defect, as it is meant to prevent lambdas in decltype
or templates, but not in sizeof.

This reverts commit 227598af47e4d46f06cfcc879f206eb34e681275.