usr.sbin/flashctl: skip lint's strict bool mode with Clang

The strict bool mode is already checked in GCC mode, so restore the
previous idiomatic code.

flashctl: enable lint's strict bool mode

No binary change.

branches: 1.2.2; 1.2.6; 1.2.10;
Add manpage for flashctl

Import the Flash and NAND subsytem code contributed by the University
of Szeged, Hungary.

The commit includes:
- Flash layer, which gives a common API to access flash devices
- NAND controller subsystem for the flash layer
- An example OMAP driver which is used on BeagleBoard or alike ARM boards

branches: 1.2.2; 1.2.6; 1.2.10;
Fix a typo, sort commands.

Add manpage for flashctl

usr.sbin/flashctl: skip lint's strict bool mode with Clang

The strict bool mode is already checked in GCC mode, so restore the
previous idiomatic code.

flashctl: fix lint's strict bool mode with Clang preprocessor

Treating the return value from the <ctype.h> character classification
functions as an 'int' is neither elegant nor idiomatic, but it works for
now.

flashctl: use consistent markup in usage message

flashctl: remove trailing whitespace

No binary change.

flashctl: unexport local functions, add CVS ID

No functional change.

flashctl: enable lint's strict bool mode

No binary change.

flashctl: fix error handling of integer arguments

Previously, flashctl accepted the command 'erase 0x 0x' as valid, even
though the numbers are not valid hex numbers.

Pointed out by lint, which complained about the wrong type conversion
for tolower, isxdigit and isdigit.

branches: 1.4.4; 1.4.8;
Properly use format strings

fix one more flash_addr_t fallout

Fix markbad command

branches: 1.1.2;
Import the Flash and NAND subsytem code contributed by the University
of Szeged, Hungary.

The commit includes:
- Flash layer, which gives a common API to access flash devices
- NAND controller subsystem for the flash layer
- An example OMAP driver which is used on BeagleBoard or alike ARM boards