Only build sysctl, vmstat, and related libraries on FreeBSD.
Change -Winline to -Wno-inline
Fixed a typo-induced bug in uhi_lock_log_disable().  Added
UHI_CLOCK_MONOTONIC_FAST to uhi_clock_gettime().
Add useless initializations to quiet spurious gcc unintialized
variable warnings.
Fix some build issues in libuinet_memstat and libuinetnv under Linux.
Some header issues remain.
Added sensible const qualifiers to parameters in the sysctl interfaces
in order to greatly reduce the number of const-defeating casts needed
in code using those interfaces.

Removed unnecessary sockaddr len initialization to improve
portability.
Increase Makefile consistency.
Updated README.