The signed characters in scripts are causing warnings with GCC 4 on
systems with proper string functions (with char*, not signed char* as
parameters). Some could be kept signed but most had to be reverted to
normal chars.

Detailed changelog:

mconf.c:
	- buf/bufptr was used in vsprintf() so it couldn't be signed.
confdata.c:
	- conf_expand_value() used strchr() and strncat() forcing
	  "normal" strings.
conf.c:
	- line was used with several string functions so it couldn't be
	  signed.
	- strip() uses strlen() so same thing there.

Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>