Various fixes to the load() function.

• Use getline() instead of fgetln(). This ensures the returned string is always null-terminated without losing the last character if the last line in a file doesn't have a newline. Also, while fgetln says the returned buffer can be modified, that doesn't actually seem safe as the current implementation means you are modifying stdio's internal buffer.

• Remove a spurious if before an ATF_REQUIRE that was clearly supposed to be non-optional.

• Remove a pointless compare of 'ptr' against '\0' (really NULL) that duplicated the middle condition in the for().

• Once a comment is found, skip the rest of the line, not just the current word.

Reviewed by: kevans
Obtained from: CheriBSD
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D26278