Makefile: Add a V=3 verbosity setting.

Prior to this commit there was an unfortunate disagreement between the seL4
project build system and the kernel's Makefile. V=3 was interpreted as maximum
verbosity by the project build system and minimum verbosity by the kernel's
Makefile. This commit makes V=3 the maximum verbosity for both.

JIRA: VER-159
ia32: Handle spurious IRQs correctly on the PIC
trivial: style
syscall stub generator: change CapDataType into a generic BitFieldType for using bitfield generated types in generated invocations
Merge branch 'master' into experimental