remove str(n)dupa usages

remove str(n)dupa usages

str(n)dupa are GNU extensions that duplicate a string, using an alloca'd
buffer. This patch removes their definitions from e.h (which should only
contain E's own API, without fallback definitions for libc functions)
which were wrong anyway (they failed in cases where str(n)dupa was an
actual function, not a macro).

Instead, we replace them depending on context with alloca+memcpy+strlen
or a static buffer (used in contexts where we are sure that the buffer
will contain the string entirely)

@fix