Fix GLIBC > 2.4 dependency regression of commit 613e33ee8ffc1f2b9c5db1e1b5bb5253a159ed6d

Commit 613e33ee8ffc1f2b9c5db1e1b5bb5253a159ed6d introduced 'memcpy' usage in Xmisc.c which could create a GLIBC > 2.4 dependency.
Include GlueGen's glibc-compat-symbols.h to remove such dependency.