MFH: r424292

• Add GCC option, turned on by default, to force compilation using GCC, this fixes a problem in zathura which shows up only when girara is compiled wth clang [1]
• Make the port use gnu99 C standard to allow it to compile with the default gcc 4.8
• Remove USES=compiler since it's not needed anymore
• Small cosmetic change to the REINPLACE_CMD lines
• While here, make the build verbose

PR: 213595
Submitted by: Michael Danilov <mike.d.ft402@gmail.com>

Approved by: ports-secteam (feld)