[ELF] - EhFrame.cpp: cover personality encoding handling code with the test cases.

CIEs augmentation string can have 'P' character,
what means the next byte is the personality encoding, a DW_EH_PE_xxx value.
This is followed by a pointer to the personality function.

We had the support of the different encodings earlier, but had no test cases.

This change adds coverage of DW_EH_PE_absptr/DW_EH_PE_signed/DW_EH_PE_udata2/DW_EH_PE_sdata2 and
DW_EH_PE_udata8/DW_EH_PE_sdata8 cases for place below:
https://github.com/llvm-mirror/lld/blob/master/ELF/EhFrame.cpp#L123

llvm-svn: 335969