[sanitizer_common] Implement popen, popenve, pclose interceptors

Implement the interceptors for popen(), pclose() and popenve()
functions.  The first two are POSIX, the third one is specific
to NetBSD.  popen() spawns a process and creates a FILE object piping
data from/to that process.  pclose() closes the pipe and waits for
the process to terminate appropriately.

For the purpose of popen(), the COMMON_INTERCEPTOR_FILE_OPEN macro is
modified to allow null path parameter.

Differential Revision: https://reviews.llvm.org/D56157

llvm-svn: 350232