MFH: r441310

• Unbreak the build: the problem was caused by header file named limits.h' present in the source tree which, with -I. option passed to the compiler, would sometimes be picked up instead of expected /usr/include/limits.h'. Fix this by renaming local header file with a `${PORTNAME}_' prefix;
• Convert CPPFLAGS/LDFLAGS/MAKE_ENV variables to USES+=localbase;
• Rewrite condition expression in standard syntax to get rid of dependency on `shells/bash', and wrap an overly long line while I'm here.

Approved by: ports-secteam (with hat)